Ultrasonic inspection device and ultrasonic inspection method

Abstract

To provide an ultrasonic inspection device that has excellent defect detection performance, for example. detectable defect size of which is small, and enables detection of even a minute defect.SOLUTION: An ultrasonic detection device Z comprises a scanning measurement device 1 and a control device 2. The scanning measurement device 1 includes: a line focusing type transmission probe 110 for emitting an ultrasonic beam; and a reception probe 140 or 121 for receiving an ultrasonic beam. The transmission probe 110 emits an ultrasonic beam upon application of a repeating-wave-packet voltage waveform composed of wave packets each including two or more waves. The transmission probe 110 is driven by an excitation frequency higher than a resonance frequency of the transmission probe 110. A signal processing unit 250 of the control device 2 includes a filter unit 240 which reduces at least a maximum intensity frequency component of the received signals of the reception probe 140 or 121, and which detects a skirt component other than the maximum intensity frequency component of a basic waveband including the maximum intensity frequency component.SELECTED DRAWING: Figure 10

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 has a defect (cavity, etc.) with low acoustic impedance such as air inside, a gap in acoustic impedance occurs inside the object, so the amount of transmitted ultrasonic beam is small. Therefore, by measuring the amount of transmitted ultrasonic beam, it is possible to detect defects inside the object.

[0003] The technology described in Patent Document 1 is known for an ultrasonic inspection device. In the ultrasonic inspection device described in Patent Document 1, a rectangular wave burst signal consisting of a predetermined number of consecutive negative rectangular waves is applied to a transmitting ultrasonic probe arranged to face the object through the air. The ultrasonic waves propagated through the object are converted into a transmitted wave signal by a receiving ultrasonic probe arranged to face the object through the air. The presence or absence of a defect in the object is determined based on the signal level of this transmitted wave signal. In addition, the transmitting ultrasonic probe and the receiving ultrasonic probe have a lower acoustic impedance of the transducer and the front panel attached to the ultrasonic transmission and reception side of the transducer than a contact type ultrasonic probe that is used by abutting against the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-128965 A Summary of the Invention [Problem to be solved by the invention]

[0005] The ultrasonic inspection device described in Patent Document 1 has a problem in that it is difficult to detect a minute defect in an object to be inspected. In particular, when the size of the defect to be detected is smaller than the ultrasonic beam, it becomes difficult to detect the defect. The problem to be solved by the present disclosure is to provide an ultrasonic inspection device and an ultrasonic inspection method that have high detection performance for defective parts, for example, a small detectable defect size, making it possible to detect even minute defects. [Means for solving the problem]

[0006] The ultrasonic inspection device disclosed herein is an ultrasonic inspection device that inspects an object to be inspected by irradiating an ultrasonic beam to the object to be inspected through a fluid, and includes a scanning and measuring device that scans and measures the ultrasonic beam on the object to be inspected, and a control device that controls the driving of the scanning and measuring device, the scanning and measuring device includes a line-focus type transmitting probe that emits the ultrasonic beam, and a receiving probe that is installed on the opposite side of the transmitting probe with respect to the object to be inspected and receives the ultrasonic beam, the transmitting probe emits an ultrasonic beam by applying a voltage waveform of a repeating wave packet composed of a wave packet with a wave number of two or more, and drives the transmitting probe at an excitation frequency higher than the resonance frequency of the transmitting probe, the control device includes a signal processing unit, the signal processing unit includes a filter unit that reduces at least the maximum intensity frequency component of the received signal of the receiving probe, and the filter unit detects a base component other than the maximum intensity frequency component of a fundamental wave band including the maximum intensity frequency component. Other solutions will be described later in the description of the embodiment of the invention. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide an ultrasonic inspection device and an ultrasonic inspection method that have high detection performance for defective parts, for example, a small detectable defect size, making it possible to detect even minute defects. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing the configuration of an ultrasonic inspection device according to a first embodiment. [Diagram 2] FIG. 10 is a diagram illustrating a transmission sound axis in the case of a point-focused transmission probe. [Diagram 3] FIG. 13 is a diagram showing a schematic view of a transmission acoustic axis plane in the case of a line focus type transmission probe. [Figure 4A] FIG. 2 is a schematic cross-sectional view showing the structure of a transmission probe, as viewed from the y-axis direction. [Figure 4B] FIG. 2 is a schematic cross-sectional view showing the structure of a transmission probe, as viewed from the x-axis direction. [Diagram 5] 3 is a diagram illustrating the long axis and scanning direction of a transmission probe; FIG. [Figure 6] FIG. 11 is a diagram illustrating the long axis and scanning direction of a transmitting probe in another embodiment. [Figure 7A] FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time when the ultrasonic beam is incident on a healthy part. [Figure 7B] FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time of incidence on a defect portion. [Figure 8A] This is a diagram showing the interaction between a defect in an object to be inspected E and an ultrasonic beam, and is a side view showing the reception of a direct ultrasonic beam. [Figure 8B] This is a diagram showing the interaction between a defect in an object to be inspected E and an ultrasonic beam, and is a top view showing the reception of a direct ultrasonic beam. [Figure 9A] FIG. 2 is a schematic diagram showing a scattered wave, which is an ultrasonic beam that has interacted with a defect, as viewed from the side. [Figure 9B] FIG. 2 is a schematic diagram showing a scattered wave, which is an ultrasonic beam that has interacted with a defect, as viewed from above. [Figure 10] FIG. 2 is a functional block diagram of a control device. [Figure 11] FIG. 13 is a diagram showing signal strength when a transmitting probe and a receiving probe are scanned across a defect in an object under test. [Figure 12] FIG. 2 is a diagram showing an example of the spectrum of a received signal observed in this embodiment. [Figure 13] 1 is a diagram illustrating a schematic distribution (frequency spectrum) of frequency components of a received signal. [Figure 14] 1 shows a voltage waveform of a burst wave applied to a transmitting probe. [Figure 15A] 4 shows the frequency spectrum of the transmitted ultrasound when the wave number is changed. [Figure 15B] These are frequency spectra when the wavenumber is 3 (dashed line), 5 (solid line), and 10 (dotted line). [Figure 16] FIG. 2 is a diagram illustrating a frequency spectrum of a fundamental wave band. [Figure 17] FIG. 1 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental waveband and the wavenumber. [Figure 18A] This shows the frequency characteristics of the gain in a band-stop filter. [Figure 18B] FIG. 10 is a diagram illustrating the frequency characteristics of a signal after processing by a band-stop filter. [Figure 19A] This shows the frequency characteristics of the gain in a low-pass filter. [Figure 19B] FIG. 2 is a diagram illustrating a frequency characteristic of a signal after processing by a low-pass filter. [Figure 20A] This shows the frequency characteristics of the gain in a high-pass filter. [Figure 20B] FIG. 10 is a diagram illustrating the frequency characteristics of a signal after processing by a high-pass filter. [Figure 21] FIG. 2 is a block diagram showing a digital filter section; [Figure 22] FIG. 13 is a block diagram showing a filter unit according to another embodiment. [Figure 23A] The wave number of the wave packet and the frequency spectrum of the fundamental wave band of the ultrasonic beam. [Figure 23B] 23B is a diagram showing how the full width at half maximum of the fundamental wave band of the spectrum shown in FIG. 23A changes with respect to the wave number N0 of the wave packet. [Figure 24] FIG. 11 is a functional block diagram of a control device in an ultrasonic inspection device according to a second embodiment. [Diagram 25] FIG. 11 is a functional block diagram of a control device in an ultrasonic inspection device according to a third embodiment. [Figure 26] FIG. 13 is a functional block diagram of a control device in an ultrasonic inspection device according to a fourth embodiment. [Figure 27A] FIG. 13 is a diagram 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 fifth embodiment. [Figure 27B] FIG. 13 is a diagram 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 fifth embodiment. [Figure 28] 4A and 4B are diagrams illustrating the relationship between a beam incident area in a transmitting probe and a beam incident area in a receiving probe. [Figure 29] FIG. 13 is a diagram showing the configuration of an ultrasonic inspection device in a sixth embodiment. [Diagram 30] FIG. 2 is a plan view showing the relative positional relationship between a transmitting probe and a receiving probe. [Diagram 31] FIG. 13 is a functional block diagram of a control device in an ultrasonic inspection device according to a sixth embodiment. [Figure 32A] FIG. 2 is a diagram for explaining 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. [Figure 32B] 1 is a diagram for explaining a transmission sound axis, a reception sound axis, and an eccentric distance, in which the transmission sound axis and the reception sound axis extend at an angle. FIG. [Diagram 33] FIG. 13 is a diagram showing the configuration of an ultrasonic inspection device in a seventh embodiment. [Diagram 34] 13A to 13C are diagrams for explaining the reason why the seventh embodiment has an effect. [Diagram 35] FIG. 13 is a diagram showing the configuration of an ultrasonic inspection device in an eighth embodiment. [Diagram 36] 4 is a plan view showing the positional relationship between a receiving probe and a sound wave shielding member. FIG. [Figure 37] FIG. 13 is a diagram illustrating a configuration of a signal processing unit in a ninth embodiment. [Figure 38]1 is a plan view showing the positional relationship between an ultrasonic beam emitted from a line-focus type transmission probe and an ultrasonic beam emitted from a point-focus type transmission probe. FIG. [Figure 39A] FIG. 13 is a diagram showing a defect image forming process. [Figure 39B] FIG. 39B shows a step performed subsequent to the step shown in FIG. 39A. [Figure 39C] FIG. 39C shows a step performed following the step shown in FIG. 39B. [Diagram 40] FIG. 23 is a diagram showing the configuration of a line focus type transmission probe in a tenth embodiment. [Diagram 41] FIG. 13 is a timing diagram showing a drive sequence in a configuration using two unit probes. [Diagram 42] FIG. 23 is a timing diagram showing a driving sequence in another embodiment related to the tenth embodiment. [Diagram 43] FIG. 23 is a functional block diagram of a control device according to an eleventh embodiment. [Figure 44A] 1 is an example of a database. [Figure 44B] FIG. 44B is a three-dimensional view of the database shown in FIG. 44A. [Diagram 45] FIG. 2 is a diagram illustrating a configuration example of an operation screen of an ultrasonic inspection device according to an example of the present disclosure. [Figure 46] FIG. 23 is a functional block diagram of an ultrasonic inspection device according to a twelfth embodiment. [Figure 47] FIG. 23 is a diagram showing the configuration of an ultrasonic inspection device in a thirteenth embodiment. [Figure 48] FIG. 2 is a diagram illustrating a hardware configuration of a control device. [Figure 49] 4 is a flowchart showing an ultrasonic inspection method according to each of the above embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a form for carrying out the present disclosure (referred to as an embodiment) 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 following one embodiment, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. In addition, the same symbols will be used for the same members, and duplicate descriptions will be omitted. Furthermore, the same names will be used for members having the same functions. The contents shown are merely schematic, and for the sake of illustration, changes may be made from the actual configuration within a range that does not significantly impair the effects of the present disclosure, and some members may be omitted or modified between drawings. In addition, the same embodiment does not necessarily need to have all the configurations.

[0010] (First embodiment) Fig. 1 is a diagram showing the configuration of an ultrasonic inspection device Z of 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 a left-right direction on the paper, a y-axis as a direction perpendicular to the paper, and a z-axis as a top-bottom direction on the paper.

[0011] The ultrasonic inspection device Z inspects an object E by irradiating an ultrasonic beam U (described later) to the object E through 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 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 E to be inspected with an ultrasonic beam U, and includes a sample stage 102 fixed to a housing 101, on which the object E to be inspected is placed. It is more preferable that the object E to be inspected is fixed to the sample stage 102 with a fixture (not shown) so as not to move. If the object E to be inspected is sufficiently heavy and does not move inadvertently, a fixture is not necessary. The object E to be inspected is made of any material. The object E to be inspected is, for example, a solid material, more specifically, for example, a metal, glass, a resin material, or a composite material such as CFRP (Carbon-Fiber Reinforced Plastics). In the example of FIG. 1, the object E to be inspected has a defective portion D inside. The defective portion D (defect) is a cavity, etc. Examples of the defective portion D are a cavity, a foreign material different from the material that should be, etc. In the object E to be inspected, a portion other than the defective portion D is called a healthy portion N.

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

[0014] The scanning measurement device 1 has a line focus type (linear convergence type, the definition of which will be described later) 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 a housing 101 via a transmitting probe scanning unit 103, and emits an ultrasonic beam U. The transmitting probe 110, details of which will be described later, emits the ultrasonic beam U when a voltage waveform of a repeating wave packet composed of wave packets with a wave number N0 of 2 or more is applied to it. The transmitting probe 110 is driven at an excitation frequency fex that is higher than the resonant frequency (natural frequency fres) of the transmitting probe 110.

[0015] The receiving probe 121 is a receiving probe 140 (coaxially arranged receiving probe) that is arranged coaxially with the transmitting probe 110 (the eccentric distance L described later is zero) and is placed on the opposite side of the transmitting probe 110 with respect to the object E to receive the ultrasonic beam U. Therefore, in the present disclosure, the eccentric distance L (distance described later) between the transmitting sound axis plane 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.

[0016] Here, "the opposite side of the transmitting probe 110" means, of the two spaces separated by the subject E, the space opposite the space in which the transmitting probe 110 is located (the opposite side in the z-axis direction), 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).

[0017] When using the line focus type transmission probe 110 as in this embodiment, the ultrasonic beam U is irradiated over a wider area when scanning in a direction perpendicular to the long axis direction of the ultrasonic beam U, compared to the case where a point focus type (point convergence type, described later) transmission probe 119 (described later) is used. By using the line focus type transmission probe 110, the time required for inspection can be significantly reduced. In other words, since a wide sweep area S can be scanned in one go, the measurement can be significantly sped up.

[0018] On the other hand, when a line focus type transmission probe 110 is used, it tends to be difficult to detect a minute defect D. In this embodiment, by using a configuration to be described later, it is possible to detect a minute defect D even when using a line focus type transmission probe 110. Hereinafter, when simply referring to the transmission probe 110, it refers to the line focus type transmission probe.

[0019] In the example of the present disclosure, the transmitting probe 110 is installed so that the transmitting acoustic axial plane 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 transmitting acoustic axial plane AX1 is in the normal direction of the mounting surface 1021 of the sample stage 102 for the object E to be inspected. In this way, in the plate-shaped object E to be inspected, the transmitting acoustic axial plane AX1 is disposed perpendicular to the surface of the object E to be inspected, 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. Here, the acoustic axis and the transmission acoustic axis plane are defined as described below.

[0020] However, the present disclosure is not limited to installing the transmitting probe 110 so that the transmitting acoustic axial plane AX1 is perpendicular to the mounting surface 1021 of the specimen E on the sample stage 102. The present disclosure is effective even when the transmitting acoustic axial plane AX1 is not perpendicular to the mounting surface 1021 of the specimen E on the sample stage 102. In the latter case, to accurately know the position of the defect D, the path of the transmitting acoustic axial plane AX1 may be calculated according to the inclination of the transmitting acoustic axial plane AX1 from the vertical direction.

[0021] Here, the positional relationship between the transmitting probe 110 and the receiving probe 121 will be described. The distance between the transmitting sound axial plane AX1 of the transmitting probe 110 and the receiving sound axis AX2 of the receiving probe 121 is defined as the eccentric distance L as described above. In this disclosure, the eccentric distance L is set to zero as described above. That is, the receiving probe 121 is disposed so that the transmitting sound axial plane AX1 and the receiving sound axis AX2 are coaxial. This is called a coaxial arrangement. Note that in this disclosure, the eccentric distance L is not limited to 0.

[0022] In this disclosure, the arrangement of the receiving probe 121 in which the transmission sound axis plane AX1 and the reception sound axis AX2 are coaxially arranged is called a coaxial arrangement, and the arrangement in which the two sound axes (the transmission sound axis plane AX1 and the 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 the coaxial arrangement and the eccentric arrangement as the arrangement of the receiving probe 121. Specific illustrations of the eccentric arrangement will be given later.

[0023] In this disclosure, particularly when specifying the receiving arrangement position, the coaxially arranged receiving probe 121 will be referred to as receiving probe 140 (coaxially arranged receiving probe), and the eccentrically arranged receiving probe 121 will be referred to as 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 arranged coaxially or eccentrically.

[0024] (sound axis and transmission sound axis plane) 2 is a diagram showing a schematic diagram of a transmission sound axis AX3 in the case of a point-focus type transmission probe 119. The sound axis is defined as the central axis of an ultrasonic beam U. Here, in the case of a point-focus type transmission probe 119, the transmission sound axis AX3 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmission probe 119. In other words, the transmission sound axis AX3 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmission probe 119. In the case of a point-focus type ultrasonic beam U, the convergence point P3 of the ultrasonic beam U is located on the transmission sound axis AX3.

[0025] 3 is a diagram showing a schematic view of a transmission sound axis plane AX1 in the case of a line-focus type transmission probe 110. As shown by dotted lines in FIG. 3, the transmission probe 110 is virtually divided in the long axis direction to form virtual elements 1100. If the division width is made sufficiently small, the virtual element 1100 can be considered to be similar to the point-focus type transmission probe 119, and in the virtual element 1100, a transmission sound axis AX3 and a convergence point P3 on the transmission sound axis AX3 are formed, although neither is shown in FIG. 3. However, the beam emitted from the virtual element 1100 is not converged in the y-axis direction, which is different from the point-focus type in this respect.

[0026] The plane on which the collection of the transmission sound axes AX3 of each virtual element 1100 spans is defined as the transmission sound axis plane AX1. The long axis direction here refers to a direction perpendicular to the emission direction of the ultrasonic beam U (-z direction in the illustrated example) and a direction at the same height position on the probe surface (±y direction in the illustrated example). In the case of the transmitting probe 110, the convergence line P4 of the ultrasonic beam U is located on the transmission sound axis plane AX1. The convergence line P4 is a collection of convergence points P3 formed by the virtual elements 1100.

[0027] As described below, the transmission acoustic axis plane AX1 includes refraction due to the interface of the object E. In other words, when the ultrasonic beam U emitted from the transmission probe 110 is refracted at the interface of the object E, the center (acoustic axis) of the propagation path of the ultrasonic beam U becomes the transmission acoustic axis plane AX1.

[0028] It should be noted that whether the line focus type transmission probe 110 or the point focus type transmission probe 119 is used, the physical properties of the emitted ultrasonic beam U are the same.

[0029] 1, the reception sound axis AX2 is defined as the sound axis of the propagation path of a virtual ultrasonic beam U (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 a virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.

[0030] As a specific example, a non-focus type receiving probe 121 with a flat probe surface will be described. In this case, the direction of the receiving sound axis AX2 is the normal direction of the probe surface, and the axis passing through the center point of the probe surface becomes 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.

[0031] 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 instructing 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 with each other, so that the transmitting probe 110 and the receiving probe 121 scan the object E under test 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 a signal acquired from the receiving probe 121. Note that a plane formed by two axes, the x-axis and y-axis directions which are the scanning directions of the transmitting probe 110, is called a scanning plane.

[0032] In the present 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.

[0033] In the illustrated example, gas G (one example of fluid F; liquid W (described later) may also be used) is interposed between the transmitting probe 110 and the object under test E, and between the receiving probe 121 and the object under test E. Therefore, the transmitting probe 110 and the receiving probe 121 can inspect the object under test E without contacting it, so that the relative positions in the xy plane can be changed smoothly and quickly. In other words, by interposing fluid F (gas G) between the transmitting probe 110 and the receiving probe 121 and the object under test E, smooth scanning becomes possible.

[0034] When a local ultrasonic beam U is emitted from the transmitting probe 110, the emitted ultrasonic beam U is locally irradiated onto the object 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 changes depending on whether it is a defective part D or a healthy part N of the object E, so this configuration makes it possible to detect the defective part D.

[0035] In order to generate a localized ultrasonic beam U, a line-focus type transmission probe 110 can be used in this embodiment.

[0036] As described above, the transmitting probe 110 is of a line focus type. On the other hand, the receiving probe 121 is a probe with looser convergence than the transmitting probe 110. In the present disclosure, a non-converging probe with a flat probe face is used for the receiving probe 121. Therefore, the receiving probe 121 is a non-converging receiving probe. By using such a non-converging receiving probe 121, information on the defect portion D can be collected over a wide range.

[0037] Fig. 4A is a schematic cross-sectional view showing the structure of the transmitting probe 110, as viewed from the y-axis direction. Fig. 4B is a schematic cross-sectional view showing the structure of the transmitting probe, as viewed from the x-axis direction. For simplification, Figs. 4A and 4B only show 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.

[0038] As shown in FIG. 4A, the ultrasonic beam U emitted from the transmitting probe 110 converges in a certain direction (the x-axis direction in the example of FIG. 4A), but does not converge in a direction perpendicular to that direction, as shown in FIG. 4B. In this way, the line-focus type transmission probe 110 emits a linear ultrasonic beam U that is converged in one direction at the convergence position (convergence line P4). In the example of Figures 4A and 4B, at the focal distance position where the ultrasonic beam U converges, the ultrasonic beam U becomes a linear ultrasonic beam U extending in the y direction.

[0039] 4A and 4B have arrows indicating the x, y, and z axis directions. In accordance with common conventions, an "x" indicates an arrow pointing from the front to the back of the figure, and a double circle symbol indicates an arrow pointing from the back to the front of the figure. Arrows indicating these directions have been included as much as possible in other drawings in this specification.

[0040] (long and short axes) Regarding the shape of the focused ultrasonic beam U, the longer side is called the "long axis" or "long side", and the shorter side is called the "short axis" or "short side". In this specification, the long axis and the long side are synonymous. The short axis and the short side are also synonymous. Regarding the shape of the focused ultrasonic beam U, the length of the long axis is defined as WL (Longer width), and the width of the short axis is defined as WS (Shorter width).

[0041] The "long axis" of the transmitting probe 110 is defined as the direction of the long axis of the emitted ultrasonic beam U. That is, in this specification, the "long axis" is defined by the shape of the emitted ultrasonic beam U, regardless of the shape of the transmitting probe 110 itself. The shape of the linearly convergent ultrasonic beam U (hereinafter, referred to as a linearly convergent beam) is typically an elongated rectangular shape on the irradiation surface, but may be an ellipse. Even in the case of an ellipse, the "long axis" and the "short axis" are defined in the same way. For ease of understanding, the drawings in this specification are drawn with the x-axis direction aligned with the minor axis of the linearly focused beam as shown in Figures 4A and 4B, and the y-axis direction therefore aligned with the major axis of the linearly focused beam.

[0042] (scan axis) Hereinafter, the scanning direction of the transmitting probe 110 is referred to as a scanning axis 131 (described later). The scanning axis is preferably set to a direction that is approximately perpendicular to the long axis of the transmitting probe 110. In this case, approximately perpendicular includes not only perpendicular but also a state in which the two cross at an angle that can be considered similar to perpendicular from the viewpoint of action and effect. Therefore, the angle θ between the long axis 130, which is the axis of the longest part in the convergence part of the ultrasonic beam U emitted from the transmitting probe 110, and the scanning axis 131, which is the scanning direction of the transmitting probe 110, is preferably 60° or more and 120° or less with respect to the scanning direction.

[0043] FIG. 5 is a diagram for explaining the long axis 130 of the transmitting probe 110 and the scanning direction. As shown in FIG. 5, the angle between the long axis 130 of the transmitting probe 110 and the scanning axis 131 is an angle θ. When the transmitting probe 110 moves by Δx in the scanning direction, the sweep area S (scanning area) of the ultrasonic beam U of the part irradiated with the ultrasonic beam U accompanying the movement becomes WL sinθ×Δx. The sweep area S is the entire area of ​​the part irradiated with the ultrasonic beam U on the inspected object E by the scanning (sweeping) of the transmitting probe 110. In the case shown in FIG. 5, since θ=90°, the irradiated part becomes rectangular, and S=WL×Δx. Therefore, when θ=90°, the sweep area S becomes the widest, and the widest area can be inspected, which is preferable.

[0044] Fig. 6 is a diagram for explaining the long axis 130 of the transmitting probe 110 and the scanning direction in another embodiment. In Fig. 6, the angle θ is 60° as an example. In this case, sinθ=0.87, so the sweep area S is reduced by only 13% compared to the case where θ=90°, and the effect of the present disclosure that allows high-speed inspection can be obtained. In other words, even if θ=60°, that is, a deviation of ±30° from the perpendicular angle, can be considered as "approximately perpendicular."

[0045] As shown by the solid arrow in Fig. 5, the transmitting probe 110 scans along the scanning axis 131, and after reaching the end of the test object E in the +x-axis direction, the position of the transmitting probe 110 is moved to another y coordinate in the +y direction as shown by the dashed arrow. Next, the transmitting probe 110 scans in the scanning axis direction toward the -x direction. In this specification, the direction in which the transmitting probe 110 moves to this different y coordinate is called the secondary movement axis and is distinguished from the scanning axis. It is preferable that the secondary movement axis is perpendicular to the scanning axis.

[0046] Moreover, the scanning direction of the transmitting probe 110 may be either the positive direction or the negative direction as long as it is along the scanning axis 131. As shown in FIG. 5, it is preferable to alternate the scanning direction between the positive direction (+ direction) and the negative direction (- direction), since this shortens the moving distance of the transmitting probe 110.

[0047] 4A and 4B, the line-focus type transmission probe 110 is configured to converge the ultrasonic beam U into a line. This allows high-speed detection of a defect D in an object E to be inspected. The transmission probe 110 includes a transmission probe housing 115, and includes a backing 112, a transducer 111, and a matching layer 113 inside the transmission probe housing 115. An electrode (not shown) is attached to the transducer 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 device (not shown) and a control device 2 by a lead wire 117.

[0048] In this 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 when the matching layer 113 is provided, and is defined as the surface of the transducer 111 when 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.

[0049] Here, a conventional ultrasonic inspection method will be described as a comparative example.

[0050] FIG. 7A is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the time of incidence on a healthy part N. FIG. 7B is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the time of incidence on a defective part D. The thick solid arrows in FIG. 7A and FIG. 7B indicate the movement direction (scanning direction) of the transmitting probe 110. In the conventional ultrasonic inspection method, as described in Patent Document 1, for example, the transmitting probe 110 and the receiving probe 140 as the receiving probe 121 are arranged so that the transmitting sound axis plane AX1 and the receiving sound axis AX2 coincide (the receiving sound axis AX2 exists within the transmitting sound axis plane AX1).

[0051] As shown in Fig. 7A, when an ultrasonic beam U is incident on a healthy portion N of an object to be inspected E, the ultrasonic beam U passes through the object to be inspected E and reaches the receiving probe 140. Therefore, the received signal becomes large. On the other hand, as shown in Fig. 7B, 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.

[0052] Here, as shown in Figures 7A and 7B, the method of detecting a defect D by reducing the received signal by blocking the transmission of an ultrasonic beam U at the defect D is referred to as the "blocking method" here.

[0053] The transmitting probe 110 scans in the direction of the scanning axis 131 as described above. During scanning, the receiving probe 140 is also scanned so as to maintain the relative positional relationship between the transmitting probe 110 and the receiving probe 140. Also, instead of scanning the transmitting probe 110 and the receiving probe 140, the subject E may be scanned. That is, it is sufficient to scan the relative positions of the transmitting probe 110 and the subject E.

[0054] As described above, the scanning axis 131 is oriented approximately perpendicular to the long axis direction of the transmitting probe 110. In the case of Fig. 7A, the long axis 130 of the transmitting probe 110 extends in the y-axis direction, and therefore the scanning axis 131 extends in the x-axis direction.

[0055] Here, the example shown in FIG. 5 above will be considered again. FIG. 5 shows a case where the object E to be inspected is arranged parallel to the xy plane. As shown in FIG. 3 above, as the ultrasonic beam U advances in the z-axis direction, the beam width in the x-axis direction narrows and converges, so that the x-axis direction becomes the minor axis direction. In FIG. 5, the minor axis direction of the beam shape of the ultrasonic beam U emitted from the transmitting probe 110 is the x-axis direction, and the major axis direction is the y-axis direction. The scanning axis 131 is set to the x-axis direction. By scanning in this manner, the range of the length WL in the major axis direction of the linearly convergent beam (the area surrounded by the dotted line in FIG. 5) can be inspected in one scan, so that the object E to be inspected can be inspected at high speed.

[0056] However, when using the transmitting probe 110 in the conventional method (for example, the method of Patent Document 1), there was a problem that it was difficult to detect a minute defect D. This is because, in the blocking method used in the conventional technology, unless the size of the defect D is about half the size of the irradiation area of ​​the ultrasonic beam U, most of the ultrasonic beam U passes through places other than the defect D (healthy part N), and the ultrasonic beam U cannot be blocked sufficiently. As a result, a sufficient amount of signal change cannot be obtained.

[0057] As an example, consider a case where the length WL of the transmission probe 110 in the long axis direction is 20 mm. If the defect is 10 mm wide, half of the irradiation area of ​​the ultrasonic beam U is blocked, so a sufficient amount of signal change can be obtained. However, if the width of the defect D is 1 mm, at most only 1 mm of the 20 mm long area is blocked. In other words, the amount of signal change is at most 1 / 20, making detection difficult.

[0058] In the present disclosure, a method described below is used to enable detection of a minute defect D using a transmitting probe. This makes it possible to achieve both high-speed inspection and detectability of a minute defect D. Note that detection of a minute defect D here means being able to detect the presence of a minute defect D within the irradiation area of ​​the ultrasonic beam U, and does not necessarily include the meaning of accurately grasping the xy direction position of the minute defect D.

[0059] A problem with the conventional technology that it becomes difficult to detect a minute defect D when a line focus type transmission probe 100 is used will be described with reference to FIGS. 8A and 8B.

[0060] FIG. 8A is a diagram showing the interaction between a defect D and an ultrasonic beam U in an object E to be inspected, and is a side view of the state in which a direct ultrasonic beam U (hereinafter referred to as a "direct wave U3") is received. FIG. 8B is a diagram showing the interaction between a defect D and an ultrasonic beam U in an object E to be inspected, and is a top view of the state in which a direct ultrasonic beam U (direct wave U3) is received. The direct wave U3 will be described later. Here, we consider a case in which the size of the defect D is smaller than the width (length WL) of the ultrasonic beam U in the major axis direction. The length WL here is the width of the focused ultrasonic beam U in the major axis direction. The size of the defect D is also smaller than the width (length WS) of the ultrasonic beam U in the minor axis direction. The defect D exists within the irradiation area of ​​the ultrasonic beam U.

[0061] 8A shows the shape of the ultrasonic beam U in a minute area near the defect D, so 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. 8A is a conceptual position drawn for easy understanding, and the position and shape of the receiving probe 121 are not scaled accurately. That is, when considering the shape 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. 8A.

[0062] 8A and 8B show the case of the blocking method in which the transmission sound axis plane AX1 and the reception sound axis AX2 are aligned. When the size of the defect D is smaller than the length WL, a part of the ultrasonic beam U is blocked, so the received signal decreases, but does not become zero. For example, when the length WL is 20 mm and the diameter of the defect D is 1 mm, the amount of the beam blocked by the defect D is 5% or less, so the received signal decreases by approximately 5% or less, making it difficult to detect the defect D. In this way, when the defect D is smaller than the length WL, many ultrasonic beams U pass through without interacting with the defect D, so the detection accuracy of the defect D decreases. This is the reason why it is difficult to detect a minute defect D when using the line focus type transmission probe 110.

[0063] 9A is a diagram showing a schematic diagram of a scattered wave U1, which is an ultrasonic beam U that has interacted with a defect D, as viewed from the side. FIG. 9B is a diagram showing a schematic diagram of a scattered wave U1, which is an ultrasonic beam U that has interacted with a defect D, as viewed from above. The defect D exists within the irradiation area of ​​the ultrasonic beam U.

[0064] In this disclosure, the ultrasonic beam U that has interacted with the defect D is called the scattered wave U1. Therefore, in this disclosure, the "scattered wave U1" refers to the ultrasonic wave that has interacted with the defect D. Some of the scattered waves U1 change direction as shown in FIG. 9B. Some of the scattered waves U1 change at least one of the phase or frequency of the wave due to the interaction with the defect D, but the traveling direction does not change. An ultrasonic wave that passes through the defect D without interacting with it is called a direct wave U3. If only the scattered wave U1 can be detected, distinguishing it from the direct wave U3, it is easier to detect a small defect D. In this disclosure, the scattered wave U1 is efficiently detected by focusing on the difference in frequency.

[0065] In this embodiment, the scattered wave U1 is detected by extracting a signal component in a specific frequency range from the received waveform. In this configuration, by appropriately selecting the frequency to be detected, the direct wave U3 component extracted from the received signal can be reduced and the scattered wave U1 component can be increased. Therefore, as shown in Figures 9A and 9B, even if a linearly convergent beam is used using the transmitting probe 110, the contribution of the extracted direct wave U3 component can be kept small. On the other hand, the scattered wave U1 from the defect D is extracted from the signal, so that the defect D can be detected. In this way, in this embodiment, even a minute defect D can be detected.

[0066] As described above, 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 a minute defect D by the conventional blocking method. For this reason, the effect of the present disclosure in detecting the scattered wave U1 is great.

[0067] 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 the case of 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 smaller than those in liquid W.

[0068] In general, as the frequency of the ultrasonic beam U decreases, it becomes difficult to converge the ultrasonic beam U. Therefore, the 1 MHz ultrasonic beam U propagating through the gas G has a larger beam diameter that can be converged compared to the ultrasonic beam U in the liquid W. On the other hand, as shown in Figs. 8A and 8B above, in the blocking mode, which is the conventional method, it is difficult to detect a defect D smaller than the beam size. However, according to the present disclosure, as shown in Fig. 5 above, the proportion of the scattered wave U1 component is increased for detection, so that it is possible to detect a defect D smaller than the beam size.

[0069] (Control device configuration) FIG. 10 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 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the test subject E, for example, by driving the transmitting probe 110 and the receiving probe 121. The position measurement unit 203 measures the scanning position. The scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202. The scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.

[0070] 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.

[0071] (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 transmission frequency setting unit 213. A burst wave signal is generated by the waveform generator 211. Then, the generated burst wave signal is 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.

[0072] The waveform of the burst wave signal will be described later, but to summarize, in the first embodiment, the waveform is a repeating wave packet waveform in which a wave packet of wave number N0 is repeated at a fundamental frequency f0. That is, the transmission system 210 of the control device 2 applies a voltage waveform of a repeating wave packet composed of wave packets with a wave number N0 of 2 or more, and drives the transmission probe 110 to emit an ultrasonic beam U. At the same time, the transmission system 210 of the control device 2 drives the transmission probe 110 at an excitation frequency fes higher than the natural frequency fres of the transmission probe 110.

[0073] The transmission system 210 includes a transmission frequency setting unit 213. The transmission frequency setting unit 213 can change the fundamental frequency f0 and set the fundamental frequency f0 to an appropriate excitation frequency fex. Since one of the features of the present disclosure is a method for selecting the fundamental frequency f0, the fundamental frequency f0 after the change is called an excitation frequency fex (excitation frequency) in the sense that it is a frequency that excites the transmission probe 110.

[0074] As 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.

[0075] In general, when the transmitting probe 110 is operated at a specific frequency determined for each probe, the amplitude intensity (sound pressure) of the generated ultrasonic waves is maximized. The frequency at which this maximum occurs 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 that the vibration of the built-in piezoelectric element resonates at the natural frequency fres. That is, in this specification, the natural frequency fres is synonymous with the resonance frequency. For this reason, the transmitting probe 100 is usually used with the excitation frequency fex set equal to the natural frequency fres.

[0076] In this embodiment, the excitation frequency fex is set to a frequency shifted higher than 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 shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. That is, the transmission frequency setting unit 213 sets the excitation frequency fex to a frequency higher than the natural frequency fres of the transmitting probe 110. As a result, the transmitting probe 110 is driven at the excitation frequency fex higher than the natural frequency fres of the transmitting probe 100. By setting the excitation frequency fex to an appropriate value, the performance of the ultrasonic inspection device Z can be improved. The significance of shifting higher will be explained.

[0077] 11 is a diagram showing the signal intensity when the transmitting probe 110 and the receiving probe 121 are scanned across a defect D in an object under test E. Inside the object under test E, there is a defect D with a width of 1 mm at the position x=0.

[0078] 11 shows the result when the excitation frequency fex is set to 0.86 MHz. 0.86 MHz is a frequency 40 kHz higher than the natural frequency fres=0.82 MHz of the transmitting probe 110. The signal detected by the receiving probe 121 is filtered out in the range of 0.86 to 0.90 MHz by the filter section 240 (FIG. 10). The filtered range does not include the maximum component frequency fm=0.82 MHz, and is a frequency higher than fm. The detected frequency component is the base component W3 (described below) of the fundamental wave band W1.

[0079] In this way, under these measurement conditions, the direct wave U3 component is reduced, so the signal is small in the healthy part N, and the signal is large in the defective part D due to the scattered wave U1 component. Therefore, even a very small defective part D can be detected.

[0080] 12 is a diagram showing an example of the spectrum of a received signal observed in this embodiment. The solid line is the spectrum at a healthy portion N, and the dashed line is the spectrum at a position including a defective portion D of an object E to be inspected.

[0081] The spectrum of the healthy part N shown by the solid line is a spectrum in which the fundamental wave band W1 has a peak at the natural frequency fres = 0.82 MHz. That is, in the example of Figure 12, 0.82 MHz is the maximum component frequency fm. This is the spectrum due to the direct wave U3.

[0082] In contrast, the spectrum at the position including the defective part D indicated by the dashed line is larger than the spectrum at the healthy part N, especially at 0.86 to 0.9 MHz, among the base components W3 of the fundamental wave band W1. This is because the components due to the scattered waves U1 at the defective part D appear. For this reason, when the frequency range of 0.86 to 0.9 MHz is detected, the signal feature amount increases corresponding to the defective part D, as shown in Figure 11.

[0083] 12, the spectrum indicated by the dashed line is larger than the solid line (spectrum of the healthy part N) even at 0.75 to 0.8 MHz among the skirt components W3 on the lower frequency side than the maximum component frequency fm. Therefore, the signal feature amount may be obtained by extracting the frequency components on the lower frequency side than the maximum component frequency fm among the skirt components W3 of the fundamental wave band W1.

[0084] Alternatively, both the high-frequency side skirt component W3 and the low-frequency side skirt component W3 may be detected from the maximum component frequency fm by using a band-cut filter (described later). 12 (the spectrum at the position including the defect D), comparing the low-frequency and high-frequency side skirt components W3, the high-frequency side has a larger frequency component. Therefore, it is more preferable to detect the skirt component W3 with a frequency higher than the maximum component frequency fm.

[0085] In this embodiment, a line focus type is used for the transmitting probe 110, and a non-focus type receiving probe is used for the receiving probe 121. Since the focal length of the non-focus type receiving probe 121 is infinite, the focal length of the receiving probe 121 is longer than the focal length of the transmitting probe 110. This configuration is preferable because it can also receive scattered waves U1 scattered at a small angle by the defect D, thereby increasing information about the defect D.

[0086] Here, the meaning of the fundamental wave band W1 and the base component W3 in this disclosure will be explained.

[0087] Fig. 13 is a diagram showing a typical distribution of frequency components (frequency spectrum) of a received signal. In Fig. 13, the horizontal axis shows frequency, and the vertical axis shows component strength (intensity). The vertical axis is shown on a logarithmic scale, showing a typical wide range of intensity.

[0088] The maximum component frequency at which the component strength is maximum is defined as fm. The maximum component frequency fm is approximately equal to the fundamental frequency f0 of the burst wave transmitted from the transmission probe 110. The frequency components of the signal have a spread before and after the maximum component frequency fm, which is called the fundamental wave band W1.

[0089] A component with a frequency (N×fm) that is N times the maximum component frequency fm is a harmonic. A component with a frequency (fm / N) that is 1 / N times the maximum component frequency fm 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 written as "harmonic", it has a frequency spread. Harmonic bands and sub-harmonic bands occur due to nonlinear phenomena, and occur when the sound pressure of the ultrasonic beam U input to the test object E is extremely strong.

[0090] When gas G is interposed between the transmitting probe 110 and the object E to be inspected as in the first embodiment, it is generally difficult to introduce an ultrasonic beam U with a strong sound pressure into the object E to be inspected, so at least one of the harmonic bands or sub-harmonic bands is often not observed. Even under the conditions in the first embodiment, the harmonic bands and sub-harmonic bands were below the detection limit.

[0091] As shown in Fig. 13, the fundamental wave band W1 has a wide frequency range. The frequency components of the fundamental wave band W1 other than the maximum component frequency fm are called "foot components W3". The foot components W3 also include the side lobes of the fundamental wave.

[0092] Returning to Fig. 12 above, the spectrum shown in Fig. 12 is the spectrum of the fundamental wave band W1. This can be seen by looking at the frequency range in Fig. 12. The frequency range in Fig. 12 is 0.75 to 0.9 MHz, which is a narrow range of ±10% of the natural frequency f0 of the transmitting probe = 0.82 MHz.

[0093] As shown in Fig. 12, in the frequency range of 0.86 to 0.9 MHz, the healthy part N (solid line) has almost no frequency components, whereas the defective part D (dotted line) has frequency components. Therefore, when the frequency components of 0.86 to 0.9 MHz are detected, the signal shown in Fig. 11 above is obtained. By appropriately selecting the frequency range for detection in this way, it is possible to reduce the direct wave U3 component and extract the scattered wave U1 component. This makes it possible to detect the minute defective part D even when using the transmitting probe 110.

[0094] 12, in this embodiment, the base component W3 is increased. One of the reasons for the increase in base component W3 is that the focal length of the receiving probe 121 is longer than the focal length of the transmitting probe 110, so that more scattered wave U1 components scattered at the defect D are received.

[0095] Returning to FIG. 10, the signal processing unit 250 includes a data processing unit 201 and a receiving system 220. The receiving system 220 is a system that detects a receiving signal output from the receiving probe 121. The receiving system 220 includes a signal amplifier 222 and a filter unit 240. Thus, the control device 2 includes the signal processing unit 250, which in turn includes the filter unit 240. The signal output from the receiving probe 121 is input to the signal amplifier 222 and amplified. The signal amplified by the signal amplifier 222 (output signal from the signal amplifier 222) is input to the filter unit 240 (cutoff filter). The filter unit 240 reduces (cuts off) components of a specific frequency range of the input signal. The filter unit 240 will be described later. The output signal from the filter unit 240 is input to the data processing unit 201.

[0096] The data processing unit 201 generates signal intensity data from the signal input from the filter unit 240. In this embodiment, a peak-to-peak signal is used as a method for generating the signal intensity data. The peak-to-peak signal is the difference between the maximum and minimum values ​​of the signal. Alternatively, the signal intensity data may be generated by performing a Fourier transform and using the intensity of a frequency component in a specific frequency range.

[0097] The data processing unit 201 also receives information on the scanning position from the scan controller 204. In this manner, the value of the signal intensity data at the current two-dimensional scanning position (x, y) is obtained. By plotting the value of the signal intensity data (peak-to-peak signal amount) against the scanning position, an image (defect image) corresponding to at least one of the position and shape of the defect D is obtained. This defect image is output to the display device 3.

[0098] (Filter section 240) In the present disclosure, the filter unit 240 is defined as a control unit that performs signal processing to reduce the intensity of signal components in a predetermined frequency range. Filter processing is also defined as signal processing to reduce the intensity of signal components in a predetermined frequency range. When a received signal is decomposed into component intensities for each frequency component by Fourier transform or the like, the frequency at which the component intensity is maximum is called the maximum component frequency. The maximum intensity frequency component is the frequency component at the maximum component frequency fm. The filter unit 240 of the present disclosure reduces the intensity of signal components in the fundamental wave band W1 that includes the maximum intensity frequency component, that is, the frequency range W2 that includes the maximum component frequency fm. The distribution of component intensities for each frequency component is called a frequency spectrum.

[0099] In the first embodiment, the filter unit 240 reduces the component intensity in the cutoff frequency range including the maximum component frequency fm. That is, the filter unit 240 reduces at least the maximum intensity frequency component (component corresponding to the maximum component frequency fm) in the received signal of the receiving probe 121. Then, the filter unit 240 detects a skirt component W3 other than the maximum intensity frequency component in the fundamental wave band W1 including the maximum intensity frequency component. Since the filter unit 240 reduces the component intensity in the cutoff frequency range, the proportion of the skirt component W3 in the fundamental wave band W1 increases in the signal after passing through the filter unit 240. In this way, the detection performance of the defect portion D (particularly the detection accuracy of the shape of the defect portion D) can be improved.

[0100] FIG. 14 shows the voltage waveform of a burst wave applied to the transmitting probe 110. The horizontal axis is time, and the vertical axis is voltage. In the example of FIG. 14, ten sine waves with a fundamental frequency f0 of 0.86 MHz are applied. These ten waves are called a wave packet. The inverse 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 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 repeating wave packet made up of wave packets with a wave number N0 of 2 or more is applied to it.

[0101] In this embodiment, each wave packet is a sine wave with a fundamental frequency f0, but may be a wave other than a sine wave. For example, the wave packet may be a wave packet composed of a rectangular wave with a wave number N.

[0102] The wave number N0 of a wave packet is the number of waves (number of cycles) of fundamental frequency f0 contained in one wave packet. In the present disclosure, the wave number N0 of a wave packet is 2 or more, and it is preferable that the wave number N0 of a wave packet is 3 or more. Under the experimental conditions of this embodiment, the wave number N0 is 10 waves as described above. A waveform of a repeating wave packet that repeats wave packets is called a burst wave.

[0103] As shown in Fig. 12 above, the present disclosure is based on the new knowledge found by the inventors that, in the frequency component distribution of a received signal, the base component W3 of the fundamental wave band W1 has a higher signal change rate at the defective part D than the signal component at the maximum component frequency fm. Furthermore, it is based on the new knowledge found by the inventors that, even within the range of the fundamental wave band W1, there is a frequency range in which the signal strength of the defective part D is greater than that of the healthy part N. Based on this knowledge, the detectability of the defective part D is improved by setting an appropriate detection frequency range.

[0104] In particular, in this embodiment, a frequency component having a small direct wave U3 component is selected. In this manner, the direct wave U3 component is reduced, so that even if the transmitting probe 110 is used, a minute defect D can be detected.

[0105] (Burst wave effect) In this disclosure, the effect of applying a burst, ie, a repeating wave packet, voltage waveform to the transmitting probe 110 is described.

[0106] As described above, the present disclosure is based on the new finding that the signal change rate at the defect D is large for the frequency component (foot component W3) shifted by Δf from the maximum component frequency fm. Therefore, by narrowing the bandwidth of the fundamental wave band W1 to an appropriate width, the frequency domain of the shifted component (fm±Δf) falls within a specific domain, making it easier to detect defect information contained in the shifted component (foot component W3).

[0107] In contrast, when a single pulse or a voltage waveform of one cycle is applied, as described later, the frequency band of the transmission wave itself spreads to a wide band, and the shifted component (fm±Δf) also spreads to a wide frequency range. For this reason, it is difficult to extract and detect the frequency component shifted by Δf, as in the present disclosure. Note that a single pulse or a voltage waveform with a wave number of 1 is generally not included in a burst wave. In this specification, a burst wave is defined as one in which the wave number N constituting a wave packet is 2 or more.

[0108] In order to clarify the difference between the present disclosure using a burst wave and the conventional example using a single pulse, the conventional example of applying a single pulse will be described below.

[0109] The method of inspecting a defect D inside an object E by applying a single pulse or one cycle of a voltage waveform is known as the pulse-echo method. By measuring the time from transmission to reception of an ultrasonic beam U, the distance to the defect D can be determined.

[0110] In the pulse-echo method, the time from transmission to reception of the ultrasonic beam U is accurately measured. For this reason, the shorter the waveform of the ultrasonic beam U is, the more accurately it can be measured. For this reason, one pulse is applied and the time is measured. In other words, the wave number N0 is 1 or 1 / 2. Also, to obtain a short waveform in the time domain, the frequency domain is set to a wide band (for example, between 0 and twice the maximum component frequency fm; 0 to 2×fm). For this reason, broadband transmitting and receiving probes are usually used in the pulse-echo method.

[0111] In the conventional pulse echo method, the frequency band is set to a wide band as described above in order to obtain a short waveform in the time domain. In contrast, in the present disclosure, a specific frequency range is detected in the frequency domain, so it is preferable that the frequency band is narrowed to an appropriate range, and therefore a burst wave is used. The appropriate frequency band in the present disclosure will be described later.

[0112] Next, the relationship between the wave number N0 of the wave packet applied to the transmitting probe 110 and the frequency band of the transmitted ultrasonic waves will be described.

[0113] FIG. 15A shows the frequency spectrum of the transmitted ultrasound when the wave number N0 is changed. Here, the frequency spectrum was calculated by Fourier transforming the time waveform of the wave packet composed of wave number N0. The fundamental frequency f0 of the waves that compose the wave packet N0 is set to 0.82 MHz. FIG. 15A shows the spectrum when the wave number N0 is 1 to 3. Note that when there is a wave number of 1, it does not become a wave packet, so it is not a repeating wave packet and is not a burst wave.

[0114] In the case of wave number N0=1 shown by the dashed line, it can be seen that the frequency components of the fundamental wave band W1 are spread over a frequency range of 0 to 1.6 MHz. This corresponds to 0 to 2×fm. Therefore, as described above, it is difficult to preferentially extract signal components that are shifted from the maximum component frequency fm as in the present disclosure. The frequency spectrum of wave number N0=1 has a typical spectral shape of the pulse-echo method.

[0115] 15A, when the wave number N0 shown by the solid line is 2, the width (band) of the fundamental wave band W1 is narrowed to 1 / 2 of that when N0 = 1. Furthermore, when the wave number N0 shown by the dashed line is 3, the width (band) of the fundamental wave band W1 is narrowed to 1 / 3 of that when N0 = 1. Therefore, it becomes possible to extract signal components that are shifted from the maximum component frequency fm as in the present disclosure.

[0116] Figure 15B shows frequency spectra when the wave number N0 is 3 (dashed line), 5 (solid line), and 10 (dotted line). Note that Figure 15B shows a narrow frequency range of 0.4 to 1.2 MHz, unlike Figure 15A above. It can be seen that increasing the wave number N0 further narrows the width (bandwidth) of the fundamental wave band W1.

[0117] FIG. 16 is a diagram showing a schematic diagram of the frequency spectrum of the fundamental wave band W1. The horizontal axis is frequency, and the vertical axis is spectral intensity. Here, the bandwidth of the fundamental wave band W1 is defined as follows. The spectral intensity at the maximum component frequency fm of the fundamental wave band W1 is set to 1, and the frequency width at half that intensity is set to the full-width at half maximum (FWHM). The value obtained by normalizing the full-width at half maximum by the maximum component frequency fm is defined as the full-width at half maximum ratio (FWHM ratio). In other words, the full-width at half maximum ratio is expressed by the following equation. Full width at half maximum ratio = Full width at half maximum / fm

[0118] FIG. 17 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental waveband W1 and the wave number N0. The full width at half maximum ratio shown on the vertical axis was calculated from the frequency spectrum of FIG. 15A and FIG. 15B. When the wave number N0 shown on the horizontal axis is 1, the full width at half maximum ratio expands to 120%. When the wave number N0=2, the full width at half maximum ratio narrows to 60%. As described above, when N0=1, the frequency spectrum of the transmission wave expands to the range of 0 to 2×fm. On the other hand, when the wave number N0 is 2 or more, the effect of the present disclosure is large.

[0119] Since the signal components containing information about the defect D appear in the frequency range of fm±0.25fm, it is more preferable that the width of the fundamental wave band W1 in the frequency spectrum of the transmission wave is narrower than this. In other words, 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 maximum component frequency fm. In other words, it is preferable that the FWHM ratio is 50% or less. This can improve the detection accuracy of the defect D. Note that the maximum component frequency fm is the frequency corresponding to the maximum intensity frequency component.

[0120] As can be seen from Fig. 17, the full width at half maximum ratio (FWHM ratio) of the fundamental waveband W1 can be set to 50% or less by setting the wave number N0 of the wave packet to 3 or more. Therefore, as described above, it is more preferable to set the wave number N0 of the wave packet to 3 or more.

[0121] Detecting the base component W3 of the fundamental wave band W1 improves defect detectability. For this reason, it is preferable that the frequencies detected by the filter section 240 (FIG. 10) include frequencies in the range of (fm±0.25fm) with respect to the maximum component frequency fm. Here, "0.25fm" means 0.25 times (i.e., 25%) the maximum component frequency fm. For example, when fm=1 MHz, it refers to the range of (1±0.25) MHz, that is, the range of (0.75 to 1.25) MHz. This corresponds to making the full width at half maximum ratio 50% or less.

[0122] 17, when the wave number N0 is set to 5 or more, the full width at half maximum ratio of the fundamental wave band W1 is 30% or less. Correspondingly, it is more preferable that the frequency detected by the filter section 240 includes a frequency range of (fm±0.15fm) with respect to the maximum component frequency fm.

[0123] (narrowband probe) There are wideband and narrowband probes in the transmitting probe 110. In the wideband probe, the full width at half maximum ratio of the fundamental wave band W1 is about 70% or more (e.g., 70% or more), and in the narrowband probe, the full width at half maximum ratio is about 50% or less (e.g., 50% or less).

[0124] In the conventional pulse-echo method, a broadband probe is often used to widen the frequency band of the transmitted wave.

[0125] On the other hand, narrowband probes are advantageous for detecting frequency components of a specific frequency because the energy of ultrasonic waves is concentrated in a narrow frequency range.

[0126] As described above, in the present disclosure, it is preferable that the full width at half maximum ratio of the fundamental wave band W1 is 50% or less. From this point of view, it is further preferable that the transmitting probe 110 is a narrow band probe in the present disclosure.

[0127] (Specific Example of the Configuration of Filter Section 240) Representative examples of frequency characteristics of the filter unit 240 for achieving the effects of the present disclosure are shown below. The filter unit 240 preferably includes at least one of a band-blocking filter, a low-pass filter, or a high-pass filter. By including at least one of these, components in a frequency range including the maximum component frequency fm can be reduced. Among these, by including at least one of a low-pass filter or a high-pass filter, only one of the high frequency or low frequency is blocked, so that the program for blocking can be simplified. Furthermore, when the filter unit 240 is implemented by an electronic circuit, the circuit configuration for blocking can be simplified.

[0128] Fig. 18A shows the frequency characteristic of gain in a band-stop filter. The band-stop filter reduces components in a frequency range W2 (Fig. 18B) including the maximum component frequency fm (maximum intensity frequency component) out of a fundamental wave band W1 (Fig. 18B) including the maximum component frequency fm. The reduction rate x is the ratio G1 / G0 of the gain G0 in the transmission region to the gain G1 in the cutoff region. In the first embodiment, the reduction rate x is set to -20 dB (1 / 10) to -40 dB (1 / 100).

[0129] 18B is a diagram showing a schematic diagram of the frequency characteristics of a signal after processing with a band-stop filter. The waveform shown by the solid line and dotted line is the fundamental wave band W1. The dotted line shows the signal components before processing, and the components in the frequency range W2 shown in the dotted line are reduced by the band-stop filter. As a result, the skirt component W3 of the fundamental wave band W1 shown by the solid line can be detected.

[0130] FIG. 19A shows the frequency characteristic of the gain in a low-pass filter. By setting the cutoff frequency of the low-pass filter to a frequency lower than the maximum component frequency fm, the signal component at the maximum component frequency fm can be reduced. Here, the cutoff frequency of a filter is the frequency at the boundary between the passband that passes the signal and the attenuation band that attenuates the signal. In the first embodiment, the cutoff frequency is set to 0.78 MHz. That is, it is set to a frequency 40 kHz lower than the maximum component frequency fm. The reduction rate in the cutoff section is set to about -40 dB.

[0131] Fig. 19B is a diagram showing the frequency characteristics of a signal after processing with a low-pass filter. The dotted and solid lines have the same meanings as in Fig. 18B. By using a low-pass filter, it is possible to detect frequency components smaller than the maximum component frequency fm in the base component W3, as shown by the solid line.

[0132] 20A shows the frequency characteristic of the gain in a high-pass filter. By setting the cutoff frequency of the high-pass filter to a frequency higher than the maximum component frequency fm, the signal component at the maximum component frequency fm can be reduced.

[0133] Fig. 20B is a diagram showing the frequency characteristics of a signal after processing with a high-pass filter. The dotted and solid lines have the same meanings as in Fig. 18B. By using a high-pass filter, it is possible to detect frequency components of the base component W3 that are greater than the maximum component frequency fm, as shown by the solid line.

[0134] (Method of mounting filter section 240) The following describes a typical configuration example of a method for implementing the filter section 240. Methods for implementing the filter section 240 are roughly divided into analog methods and digital methods.

[0135] The analog method reduces signal components in a desired frequency range using an analog circuit. Typical examples of frequency characteristics of the filter unit 240 include a band-stop filter (FIGS. 18A and 18B), a low-pass filter (FIGS. 19A and 19B), and a high-pass filter (FIGS. 20A and 20B). There are various known methods for realizing analog circuits having such frequency characteristics. Therefore, any method may be used to realize the analog circuit.

[0136] 21 is a block diagram showing a digital filter unit 240. The filter unit 240 includes a frequency component conversion unit 241, a frequency selection unit 242, and a frequency component inverse conversion unit 243. The frequency component conversion unit 241 converts the received signal of the receiving probe 121 input from the signal amplifier 222 into frequency components. The frequency selection unit 242 selects the above-mentioned foot component W3 by removing a frequency band including the maximum intensity frequency component (maximum component frequency fm). The frequency component inverse conversion unit 243 returns only the necessary frequency components to a time domain signal. By including the frequency component conversion unit 241 and the frequency selection unit 242 among these, in particular, the digital filter unit 240 can be configured.

[0137] Such a digital filter unit 240 can also reduce components in a frequency range including the maximum component frequency fm. The process performed by the frequency component conversion unit 241 is a process of converting a time domain signal waveform into frequency components, typically using a Fourier transform. The process performed by the frequency component inverse conversion unit 243 is a process of converting a frequency component (frequency spectrum) into a time domain signal waveform, typically using an inverse Fourier transform.

[0138] 22 is a block diagram showing a filter unit 240 according to another embodiment. The filter unit 240 is provided in the signal processing unit 250. The filter unit 240 includes a frequency component conversion unit 241 and a frequency selection unit 242. The output of the frequency selection unit 242 is input to a signal strength calculation unit 231 in the data processing unit 201. The signal strength calculation unit 231 calculates the signal strength based on information on the frequency components.

[0139] The reason why the base component W3 of the fundamental wave band W1 changes sensitively to the defect D is considered to be as follows.

[0140] The direct wave U3, which does not interact with the defective part D, does not change in wave propagation direction, phase, frequency, etc. Therefore, the direct wave U3 accounts for a large proportion of the signal component of the maximum component frequency fm. Therefore, the change between the defective part D and the healthy part N is small.

[0141] As shown in Figures 5A and 5B above, the scattered wave U1 that interacts with the defect D has some components that change the propagation direction, and some components that do not change the propagation direction but at least one of the phase and frequency changes. In addition, some of the components that change the propagation direction also have components that change frequency. Therefore, the proportion of the scattered wave U1 components, which are the ultrasonic beam U that interacts with the defect D, in the foot component W3 of the fundamental wave band W1, which is a component shifted from the maximum component frequency fm, increases. As a result, the change between the defect D and the healthy part N becomes larger. In this way, the component of the maximum component frequency fm is reduced and the foot component W3 of the fundamental wave band W1 is detected, thereby improving the detection performance of the defect D.

[0142] (Fundamental frequency base component W3) As described above, the present disclosure improves the detection performance of the defect D by detecting the foot component W3 of the fundamental wave band W1. Therefore, increasing the foot component W3 of the fundamental wave band W1 further contributes to improving the detection performance. Therefore, the inventors have thoroughly studied the relationship of the transmitted ultrasonic waveform to increase the foot component W3 of the fundamental wave band W1.

[0143] There are two things that have the effect of increasing the amount of the tail component W3 of the fundamental wave band W1: the wave number of each wave packet that constitutes the repeating wave packet, and the selection of the excitation frequency.

[0144] (Wave number of the wave packet) First, we will show the relationship between the wave number of the wave packet that composes the repeating wave packet and the tail component. The wave number of the wave packet is the number of waves of the fundamental frequency f0 contained in one wave packet, as shown in Figure 14 above.

[0145] FIG. 23A shows the wave number N0 of the wave packet and the frequency spectrum of the fundamental wave band W1 of the ultrasonic beam U. Here, an ultrasonic wave with a fundamental frequency f0=0.82 MHz is used as an example. The frequency spectra are shown for wave packets of wave numbers N0=10 (dashed line) and N0=20 (solid line). The spectrum shown by the dashed dotted line is for a continuous wave. In the case of a continuous wave, it only has a component of the fundamental frequency f0, and the skirt component W3 is almost nonexistent. In contrast, as can be seen from the spectra for N0=20 and 10, the smaller the wave number N0, the wider the width of the fundamental wave band W1 and the larger the skirt component W3.

[0146] FIG. 23B is a diagram showing how the full width at half maximum (FWHM) of the fundamental waveband of the spectrum shown in FIG. 23A changes with respect to the wave number N0 of the wave packet.

[0147] According to the present disclosure, since the change due to the defect D is large in the foot component W3 of the fundamental wave band W1, it is preferable that the ultrasonic beam U used in the present disclosure is an ultrasonic beam U composed of a repeating wave packet, not a continuous wave. Furthermore, as shown in Fig. 23B, the smaller the wave number N0 of each wave packet, the more the foot component W3 of the fundamental wave band W1 increases, so the smaller the wave number N0, the more preferable it is. As shown in Fig. 23B, when N0≦30, the full width at half maximum spreads to 30 kHz (0.03 MHz) or more, so it is preferable that the wave number N0 of the wave packet is 30 or less.

[0148] It is not preferable that the full width at half maximum (FWHM) of the fundamental wave band W1 is too wide, and it is preferable that it is 50% or less of the maximum component frequency fm. In order to make the full width at half maximum of the fundamental wave band W1 50% or less of the maximum component frequency fm, it is preferable that the wave number N0 of the wave packet is 2 or more, and it is even more preferable that the wave number N0 is 3 or more. The reasons for this are as described above with reference to FIG. 17.

[0149] As described above, it is preferable that the wave number N0 constituting the wave packet of the burst wave is 2 or more and 30 or less. It is further preferable that the wave number N0 is 3 or more and 30 or less.

[0150] (excitation frequency fex) Next, the relationship between the excitation frequency fex and the skirt component W3 will be shown. The excitation frequency fex is a frequency that corresponds to the fundamental frequency f0 of the wave packet, and is a frequency that is applied to the transmission probe 110.

[0151] Generally, the transmitting probe 110 has a natural frequency fres (resonance frequency). The natural frequency fres of the transmitting probe 110 is the frequency at which the piezoelectric element constituting the transmitting probe 110 is most likely to vibrate. When a voltage of the natural frequency fres is applied, the intensity (acoustic energy) of the emitted ultrasonic wave becomes maximum, so that the excitation frequency fex is usually set to be equal to the natural frequency fres of the transmitting probe 110.

[0152] In contrast, in this embodiment, the excitation frequency fex is set to a frequency shifted from the natural frequency fres. Figure 12 shows the frequency spectrum when fex is set to 0.86 MHz, which is 40 kHz higher than the natural frequency fres. Here, the excitation frequency fex is set in the frequency range of the fundamental wave band W1.

[0153] Looking at the spectrum (dashed line) at the position including the defective part D in Figure 12 above, it can be seen that the amount (component strength) of the skirt component W3 of the fundamental wave band W1 is increasing. Specifically, on the lower frequency side (0.75 to 0.8 MHz) than the natural frequency fres = 0.82 MHz, it has components larger than those of the spectrum of the healthy part N (solid line). Also, on the higher frequency side than the natural frequency fres, there is a frequency component with a peak around 0.87 MHz. Here, both the components on the low frequency side and the high frequency side belong to the fundamental wave band W1. In other words, it is the skirt component W3 of the fundamental wave band W1.

[0154] As can be seen by comparing the spectrum (solid line) of the healthy part N and the spectrum (dotted line) of the defective part D shown in Fig. 12, there is a significant difference in the amount (component intensity) of the base component W3 of the fundamental wave band W1 between the healthy part N and the defective part D. This improves the detectability of the defective part D. 12, in the foot component W3 higher than the natural frequency fres or the foot component W3 lower than the natural frequency fres, the component intensity increases at the defect D. Therefore, even when the transmission probe 110 is used, it is possible to detect a minute defect D. The skirt component W3 higher than the natural frequency fres is more preferable since the increase in component strength is greater.

[0155] In this way, by setting the excitation frequency fex to a value within the frequency range of the fundamental wave band W1 and shifted from the natural frequency fres, the amount of the base component W3 of the fundamental wave band W1 increases, improving the detection performance of the defect D. Therefore, it is preferable to set the excitation frequency fex within the frequency range of the fundamental wave band W1.

[0156] As described above, it is preferable that the full width at half maximum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. Therefore, it is preferable that the excitation frequency fex is set in the range of (fres±0.25fm), where fres is the natural frequency of the transmitting probe. In other words, it is preferable that the absolute value of the difference between the excitation frequency fex and the natural frequency fres, |fex-fres|, is 25% or less of the maximum component frequency fm. In this disclosure, the natural frequency fres is synonymous with the resonant frequency.

[0157] Furthermore, when the transmitting probe 110 is driven at the natural frequency fres, the strongest ultrasonic beam U is emitted. The greater the deviation of the excitation frequency fex from the natural frequency fres, the lower the emission efficiency of the ultrasonic beam U. For this reason, it is more preferable that the absolute value |fex-fres| of the difference between the excitation frequency fex and the natural frequency fres is 15% or less of the maximum component frequency fm.

[0158] (Range of natural frequency of transmitting probe 110) A preferred range of the natural frequency fres of the transmitting probe 110 used in the present disclosure will now be described.

[0159] In the present disclosure, a local ultrasonic beam U is irradiated onto an object E to detect a defect D at that position. Therefore, it is preferable that the beam diameter of the local ultrasonic beam U is as small as possible. Therefore, it is preferable to use a convergent probe as the transmitting probe 110.

[0160] Since the ultrasonic beam U is a wave, it is known that it is difficult to converge it to less than the wavelength even if it is converged using an acoustic lens, etc. This is because the effect of wave diffraction appears.

[0161] The wavelength λ of an ultrasonic beam U with frequency f0 in a medium with sound speed c is expressed as λ = c / f0. If acrylic is taken as an example of the object E to be inspected, the sound speed c is 2730 (m / s), so the wavelength λ of the ultrasonic beam U at frequency f0 = 50 kHz is 54 mm. In other words, even if a focusing probe is used, the ultrasonic beam U with frequency f0 = 50 kHz can only be focused to about 50 mm, making it difficult to sufficiently focus it.

[0162] When the frequency f0 is 200 kHz, the wavelength λ is 14 mm, so that a focused ultrasonic beam U can be realized. For this reason, it is preferable that the natural frequency fres of the transmitting probe 110 is 200 kHz or more. In this embodiment, the natural frequency of the transmitting probe 110 is set to 0.82 MHz (820 kHz).

[0163] In the present disclosure, since the scattered wave U1 is detected, it is possible to detect a defect D smaller than the beam diameter, as shown in FIGS. 5A and 5B.

[0164] In this embodiment, each wave packet is a sine wave with a fundamental frequency f0, but it may be a wave packet other than a sine wave. For example, it may be a wave packet composed of a rectangular wave with a wave number N0.

[0165] In addition, the excitation frequency fex may be a wave having a plurality of excitation frequencies fex in one wave packet N0. As such a wave, a chirp wave whose frequency changes with time is known. Even when using a wave having a plurality of excitation frequencies fex, it is preferable that each excitation frequency fex is set within the frequency range of the fundamental wave band W1.

[0166] Second embodiment 24 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the second embodiment. In the second embodiment, the type of filter used in the filter section 240 is determined by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D before inspecting the object E. Then, the object E is inspected using the filter determined before the inspection. In this embodiment, similarly to the first embodiment, the transmitting probe 110 is driven by a burst wave.

[0167] As in the first embodiment, in this embodiment, the excitation frequency fex is set to a frequency 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 shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, it is possible to improve the performance of the ultrasonic inspection device Z of this embodiment.

[0168] The filter unit 240 includes a detection unit 244 and a determination unit 245. The detection unit 244 detects a plurality of different foot components W3 in the fundamental wave band W1 in the relationship between frequency and signal intensity (component intensity). The relationship here is, for example, the relationship shown in FIG. 12 and the like, and is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) in which the position of the defective part D is known. The determination unit 245 determines which foot component W3 to use by comparing the detected plurality of foot components W3 with each other. By configuring the filter unit 240 in this way, the foot component W3 that is easy to identify the signal change caused by the defective part D can be used, and the detection accuracy of the defective part D can be improved.

[0169] The detection unit 244 includes, for example, a filter capable of detecting different foot components W3. The filter here is, for example, at least two of the band-stop filter (FIG. 18A), the low-pass filter (FIG. 19A), and the high-pass filter (FIG. 20A). For example, when the detection unit 244 includes these three filters, the detection unit 244 detects the foot components W3 shown in FIG. 18B, the foot components W3 shown in FIG. 19B, and the foot components W3 shown in FIG. 20B using the three filters in the relationship shown in FIG. 12. The determination unit 245 then compares the three detected foot components W3 with each other, for example, by selecting the foot component W3 with the largest difference between the healthy part N and the defective part D, and determines which foot component W3 to use. The filter unit 240 uses the determined foot component W3 to inspect the object E, thereby improving the detection accuracy of the defective part D.

[0170] Third embodiment 25 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the third embodiment. In the third embodiment, before the inspection of the object E to be inspected, data obtained by irradiating an ultrasonic beam U onto a sample (not shown) whose position of a defect D is known is presented to a user, and the user decides which base component W3 to use, i.e., which filter to use.

[0171] As in the first embodiment, in this embodiment, the excitation frequency fex is set to a frequency 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 shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, it is possible to improve the performance of the ultrasonic inspection device Z of this embodiment.

[0172] The control device 2 includes a display unit 223 and a reception unit 224. In the illustrated example, the display unit 223 and the reception unit 224 are provided in the data processing unit 201. The display unit 223 displays the relationship between frequency and signal intensity (component intensity) on the display device 3. The relationship here is, for example, the relationship shown in FIG. 12 and the like, and is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not illustrated) whose position of a defective part D is known. The reception unit 224 receives information that is input by a user based on the relationship between frequency and signal intensity and indicates a foot component W3 to be detected. The input is performed through the input device 4, which is, for example, a keyboard, a mouse, a touch panel, or the like. Then, the filter unit 240 detects the foot component W3 corresponding to the information based on the information received by the reception unit 224.

[0173] By configuring the control device 2 in this way, the base component W3 to be detected can be determined based on the user's subjective judgment. This allows the user to make a judgment based on their experience, making it possible to perform an inspection that is suited to the actual inspection situation.

[0174] (Fourth embodiment) 26 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the fourth embodiment. In the fourth embodiment, the received signal is converted into frequency components by the frequency conversion unit 230 and stored, and after the measurement of the inspection, an image is generated using appropriate frequency components. This constitutes the filter unit 240. In the example of the present disclosure, the filter unit 240 is constituted by the frequency conversion unit 230 and a frequency selection unit 242.

[0175] As in the first embodiment, in this embodiment, the excitation frequency fex is set to a frequency 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 shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, it is possible to improve the performance of the ultrasonic inspection device Z of this embodiment.

[0176] The signal processing unit 250 performs signal processing to extract significant information by amplifying the signal from the receiving probe 121, selecting a frequency, etc. The signal amplified by the signal amplifier 222 is input to the frequency conversion unit 230.

[0177] The frequency conversion unit 230 is provided in the signal processing unit 250, and converts the received signal of the receiving probe 121 into frequency components (signal processing). In the example of the present disclosure, the frequency conversion unit 230 converts the received signal, which is a time domain waveform, into frequency components. The frequency components are the magnitude (spectrum) of each frequency component. Examples of frequency components include a method of expressing a combination of a real part and an imaginary part as a complex number, and a method of expressing an amplitude (absolute value) and a phase.

[0178] The conversion in the frequency conversion unit 230 can be performed by, for example, a Fourier transform. The conversion may also be performed together with the extraction of 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.

[0179] (Accumulation 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.

[0180] In the example of the present disclosure, the frequency conversion section 230 converts the time domain waveform into frequency component data and stores it together with the position information in the storage section 261. The imaging section 262 then 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, as will be described later in detail. That is, the imaging section 262 visualizes the signal feature amount based on the input frequency parameters. That is, when the test 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.

[0181] This configuration is preferable for the following two reasons. The first is the time required for calculation. The conversion process to 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 later, and the calculation time required for this is short. As a typical example, the processing is completed in 0.2 seconds or less even for measurement points of 100 rows x 100 columns.

[0182] Therefore, according to the example of the present disclosure, as described in detail below, when the frequency parameters are "updated," an updated image 273 (described below) can be obtained instantly. In this manner, by storing the frequency component data in the storage unit 261, a frequency set suitable for improving the detectability of the defect portion D can be selected in a short time.

[0183] Secondly, the amount of data is reduced. The signal waveform of the receiving probe 140 has about 100,000 points for one measurement position in the time domain waveform, whereas the frequency component data only requires complex numbers for 20 to 100 types of frequencies. That is, the amount of data for the test subject E can be reduced to about 1 / 1000. In this way, there is also the advantage that the amount of data stored in the storage unit 261 can be significantly reduced.

[0184] The data processing unit 201 also receives information on the scanning position from the scan controller 204. In this manner, data on 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 of the defect D is created by determining a signal feature amount determined from the frequency component data for each scanning position.

[0185] The frequency component data is frequency components 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 described above, it is more preferable that the frequency components include phase information in addition to the amplitude (absolute value). This is equivalent to treating the frequency components as complex numbers. As described below, by including phase information, it is possible to calculate signal features with higher performance.

[0186] 26, 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 later) indicating the position (defect position) of a defect D by using a portion of the converted frequency components that is designated by a frequency parameter. 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 manner, the image 273 can be generated.

[0187] The change in the signal (change in the received signal) referred to here is a signal feature amount in the example of the present disclosure. Therefore, the imaging unit 262 first calculates the signal feature amount from the part of the frequency spectrum corresponding to the converted frequency component that is the input frequency parameter. The signal feature amount is, for example, a value that represents the change in the signal as described above, and is a value calculated from frequency component data so as to appropriately include defect information (for example, the position of the defect part D), although the calculation method will be described later. A specific example of the calculation method of the signal feature amount will be described later. By plotting the signal feature amount thus obtained against the scanning position (x, y), a two-dimensional image (defect image) of the defect part D present inside the inspected object E is generated.

[0188] The above procedure is performed while changing the scanning position (x, y) to scan a desired range. When the scanning is completed, the frequency component data and signal feature amount 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 amount is calculated every 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 amount may be calculated collectively after the measurement to generate a defect image.

[0189] (Calculation of signal features) A method for calculating signal features from frequency component data used in the examples of the present disclosure will be described. In this example, to make the formula easier to understand, frequency f is expressed as angular frequency ω, which is frequency f multiplied by 2π. Also, j represents the imaginary unit.

[0190] The process of calculating frequency components H(ω) from the measured signal waveform h1(t) in the time domain is shown. This is an example of a method of processing the output signal of the signal amplifier 222 in FIG.

[0191]

number

[0192] Here, tk is a time sequence spaced at the appropriate sampling frequency. k is zero or a finite positive integer (k=0,1,2,...). Equation (1) performs a process roughly equivalent to integration over the time range to be summed. Equation (1) gives the frequency component H(ω).

[0193] An appropriate sampling frequency is a frequency that satisfies the commonly known sampling theorem. In other words, the sampling frequency is set to a frequency that is at least twice the frequency band of the signal to be observed. In addition, 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.

[0194] 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.

[0195] 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).

[0196]

number

[0197]

number

[0198] Here, in equation (2), j is the imaginary unit, and in equation (3), Re[ ] is a process for 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.

[0199] In formula (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 in the form of a frequency range. The frequency parameter may be set in advance. The frequency parameter may be input by the user.

[0200] h(t) obtained by formula (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 a signal feature. In the example of the present disclosure, the difference between the maximum and minimum values ​​(Peak-to-Peak value) is abbreviated as PP value.

[0201] In formula (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 account the phase information of the frequency component H(ω). This is more preferable because it allows the signal feature quantity to accurately reflect the position information of the defect part D.

[0202] The selection of the frequency parameter, i.e., the set of frequencies {ω} to be included in the accumulation in equation (2), is important. The maximum component frequency fm is excluded from the set of frequencies {ω} to be included in the accumulation. In this way, a filter section 240 that reduces the maximum intensity frequency component can be configured. Furthermore, the frequencies to be included in the accumulation include the frequency of the base component W3 of the fundamental wave band W1. This can improve the detectability of the defect D in the object E to be inspected. Furthermore, it is even more effective to also exclude frequency components in the vicinity of the maximum component frequency fm.

[0203] Since the angular frequency ω can be converted to the frequency f using the relationship ω = 2πf, we will make appropriate conversions and interpretations. For example, when we write "excluding the maximum component frequency fm from the frequency set {ω}," it means "excluding ωm = 2πfm."

[0204] The maximum component frequency fm is the frequency at which the spectrum of the fundamental wave band W1 of the received signal is at a maximum, and in this disclosure, it is defined as the frequency at which it is approximately at a maximum.

[0205] In addition, in formula (2), the set of frequencies {ω} to be included in the accumulation may include only frequencies lower than the maximum component frequency fm. This allows the filter unit 240 to have low-pass filter characteristics. Similarly, only frequencies lower than the maximum component frequency fm may be included.

[0206] The frequency parameters are appropriately set in the frequency selection section 242. In this manner, the frequency conversion section 230 and the frequency selection section 242 form a filter section 240.

[0207] The frequency parameters may be set appropriately before the test, may be changed after the measurement, or may be set by the user.

[0208] The signal feature amount may be a value calculated from frequency component data so as to appropriately include the position information of the defect portion D, and is not limited to the above calculation method. In the above example, the PP value of the signal waveform h(t) in the time domain is used as the signal feature amount, but the absolute value of h(t) may be calculated, and the area of ​​h(t) may be calculated as the signal feature amount. Here, the procedure for calculating the area may involve sampling h(t) at appropriate time intervals and calculating the sum of h(t) at the sampling points. Also, instead of the absolute value of h(t), the square value of h(t) may be used. Furthermore, instead of using formulas (2) and (3), the absolute values ​​of the frequency components H(ω) may be summed up for the input frequency set {ω} and used as the signal feature amount.

[0209] (Fifth embodiment. Focal length of the receiving probe 121) In the fifth 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 it allows more components of the scattered wave U1 to be detected, as described below. 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 components, the easier it is to detect the defect D.

[0210] FIG. 27A is a diagram showing a schematic diagram of a propagation path of an ultrasonic beam U in the fifth embodiment when the focal length R1 of the transmitting probe 110 and the focal length R2 of the receiving probe 121 are equal. Both the transmitting probe 110 and the receiving probe 121 are line focus types, and FIG. 27A is a diagram showing the convergence of the ultrasonic beam U from the side. However, the receiving probe 121 may be a point focus type or a non-converging type. The receiving probe 121 can detect the ultrasonic beam U within the range of a cone (shape) C2 of a virtual beam virtually emitted from the receiving probe 121. In the example shown in FIG. 27A, the convergence line of the ultrasonic beam U transmitted from the transmitting probe 110 and the convergence line 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.

[0211] FIG. 27B is a diagram showing a schematic diagram of a 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 fifth embodiment. The receiving probe 121 can detect an ultrasonic beam U within a range of a cone (shape) C3 of a virtual beam virtually emitted from the receiving probe 121. Therefore, even if a scattered wave U1 (not shown in FIG. 27B) whose propagation direction is slightly changed by a defect D is within the range of the cone C3, it can be detected. 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.

[0212] 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.

[0213] 28 is a diagram for explaining the relationship between the beam incidence area T1 in the transmitting probe 110 and the beam incidence area T2 in the receiving probe 121. The beam incidence area T1 of the transmitting probe 110 on the object E to be inspected is the intersection area of ​​the ultrasonic beam U emitted from the transmitting probe 110 on the surface of the object E to be inspected. The beam incidence area T2 of the receiving probe 121 is the intersection area of ​​the virtual ultrasonic beam U2 on the surface of the object E to be inspected, assuming that the ultrasonic beam U is emitted from the receiving probe 121.

[0214] 28, the path of the ultrasonic beam U is shown 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, in the side view (lateral view) shown in FIG. 28, the beam incidence area T2 of the receiving probe 121 at the object under test E is larger than the beam incidence 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 that of the transmitting probe 110.

[0215] 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 distance from the test subject E to the transmitting probe 110 and the receiving probe 121 is, for example, the same for both, but does not have to be the same.

[0216] In the example of the present disclosure, the convergence of the receiving probe 121 is set to be looser than that of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set to be 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, so that 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.

[0217] 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 manner, the receiving probe 121 can more easily receive the scattered wave U1, and the scattered wave U1 can more easily be detected.

[0218] In addition, a non-converging probe (not shown) may be used as the receiving probe 121 as a configuration in which the focal length R2 of the receiving probe 121 is 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 non-converging receiving probe 121, the convergence of the receiving probe 121 is looser than the convergence of the transmitting probe 110.

[0219] Sixth embodiment 29 is a diagram showing the configuration of an ultrasonic inspection device Z in the sixth embodiment. In the sixth embodiment, the transmission acoustic axis plane AX1 of the transmitting probe 110 and the reception acoustic axis AX2 of the receiving probe 121 are arranged to be offset from each other. That is, the receiving probe 121 in the sixth embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception acoustic axis AX2 arranged at a position different from the transmission acoustic axis plane AX1 of the transmitting probe 110. Therefore, the eccentric distance L (distance) between the transmission acoustic axis plane AX1 (acoustic axis plane) of the transmitting probe 110 and the reception acoustic axis AX2 (acoustic axis) of the receiving probe 120 is greater than zero.

[0220] Such an arrangement makes it possible to detect scattered waves U1 whose spatial direction has changed. In this embodiment, the direct wave U3 travels along the transmission acoustic axis plane AX1 and does not enter the receiving probe 121. Therefore, even if the irradiation area of ​​the ultrasonic beam U is increased by using the transmitting probe 110, the scattered wave U1 component caused by the defect D can be effectively detected. In this way, the transmitting probe 110 can be used to detect a minute defect D.

[0221] FIG. 30 is a plan view showing the relative positional relationship between the transmitting probe 110 and the receiving probe 121. In FIG. 30, the receiving probe 121 is shown by a dotted line because it is located on the opposite side of the transmitting probe 110 with the object under test E in between. The eccentric distance L between the transmitting sound axis plane AX1 of the transmitting probe 110 and the receiving sound axis AX2 of the receiving probe 121 is arranged to be greater than zero. Here, the receiving probe 121 is arranged at a position shifted in a direction substantially perpendicular to the long axis direction of the transmitting probe 110 (y-axis direction in the figure). By arranging in this way, even if the defect part D is located at any position of the linearly convergent beam with a length W2 in the long axis direction, the scattered wave U1 can be received. Note that the scanning axis 131, which is the direction in which the transmitting probe 110 is scanned, intersects the long axis 130 of the transmitting probe 110 in a direction substantially perpendicular to the long axis 130.

[0222] 31 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the sixth embodiment. In this embodiment, the position of the receiving probe 121 is shifted from the transmission sound axis plane AX1. This reduces the direct wave component, so there is no need to provide a filter section. Therefore, the signal is input directly from the signal amplifier 222 to the data processing section 201.

[0223] In the healthy portion N, the ultrasonic beam U emitted from the transmitting probe 110 does not reach the receiving probe 121, and therefore the ultrasonic beam U is not observed as a received signal. Since a scattered wave U1 component is generated in the defective portion D, the scattered wave U1 is incident on the receiving probe 121, and a signal component is detected. In this manner, in this embodiment, the position of the receiving probe 121 is shifted to spatially prevent the detection of the direct wave U3, so that the scattered wave U1 component can be extracted without providing a filter section. As a result, even if the transmitting probe 110 is used, a minute defective portion D can be detected.

[0224] In this embodiment, the excitation frequency fex does not need to be shifted from the natural frequency of the transmission probe 110 either.

[0225] 31, a configuration may be used in which the eccentric distance L of the receiving probe 121 is set to be greater than zero, and an appropriate frequency range is extracted and detected using the filter section 240. This provides an even greater effect, since the direct wave U3 is reduced in both a spatial manner and a frequency manner.

[0226] Fig. 32A is a diagram for explaining the transmission sound axis plane AX1, the reception sound axis AX2, and the eccentric distance L, in the case where the transmission sound axis plane AX1 and the reception sound axis AX2 extend vertically. Fig. 32B is a diagram for explaining the transmission sound axis plane AX1, the reception sound axis AX2, and the eccentric distance L, in the case where the transmission sound axis plane AX1 and the reception sound axis AX2 extend at an angle. Figs. 32A and 32B also show the receiving probe 140 (coaxially arranged receiving probe) by dashed lines for reference.

[0227] The direction of the receiving sound axis AX2 is the normal direction of the probe surface 114 (FIG. 4A). This is because a 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 be received with good sensitivity.

[0228] The eccentric distance L is defined as the deviation distance between the transmission sound axis plane AX1 and the reception sound axis AX2. Therefore, as shown in FIG. 32B, when the ultrasonic beam U emitted from the transmission probe 110 is refracted, the eccentric distance L is defined as the deviation distance between the refracting transmission sound axis plane AX1 and the reception sound axis AX2. In the ultrasonic inspection device Z of the sixth embodiment, the transmission probe 110 and the reception probe 120 are adjusted by a distance adjustment unit 105 (FIG. 29) that adjusts the eccentric distance L so that the eccentric distance L defined in this way becomes a distance greater than zero. The distance adjustment unit 105 is provided in the ultrasonic inspection device Z, and adjusts the eccentric distance L between the transmission sound axis plane AX1 of the transmission probe 110 and the reception sound axis AX2 of the reception probes 121 and 120 to a distance greater than zero.

[0229] FIG. 32A shows a case where the transmitting probe 110 is arranged in the normal direction on the surface of the object E to be inspected. In FIG. 32A and FIG. 32B, the transmitting sound axis plane AX1 is indicated by a solid arrow. Also, the receiving sound axis AX2 is indicated by a dashed arrow. In FIG. 32A and FIG. 32B, the position of the receiving probe 121 indicated by the broken line is a position where the eccentric distance L is zero, and the receiving probe 121 where the transmitting sound axis plane AX1 and the receiving sound axis AX2 coincide is the receiving probe 140 as a coaxially arranged receiving probe. Also, the receiving probe 121 indicated by the solid line is the receiving probe 120 (eccentrically arranged receiving probe) arranged at a position with an eccentric distance L larger than zero. When the transmitting probe 110 is installed so that the transmitting sound axis plane AX1 is perpendicular to the horizontal plane (xy plane in FIG. 29), the propagation path of the ultrasonic beam U is not refracted. In other words, the transmitting sound axis plane AX1 is not refracted. This corresponds to the case where the transmission probe 110 is installed so that the transmission acoustic axis plane AX1 of the transmission probe 110 is perpendicular to the mounting surface 1021 of the sample stage .

[0230] In this embodiment, the transmitting probe 110 is installed so that the transmitting acoustic axial plane AX1 is in the normal direction to the mounting surface 1021 of the object under test E on the sample stage 102. As described above, by doing so, in the plate-shaped object under test E, the transmitting acoustic axial plane 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.

[0231] FIG. 32B shows a case where the transmitting probe 110 is arranged at an angle α from the normal direction on the surface of the object E to be inspected. In FIG. 32B, as in FIG. 32A, the transmitting sound axis plane AX1 is indicated by a solid arrow, and the receiving sound axis AX2 is indicated by a dashed arrow. In the example shown in FIG. 32B, the propagation path of the ultrasonic beam U is refracted at a refraction angle β at the interface between the object E to be inspected and the fluid F. Therefore, the transmitting sound axis plane AX1 is bent (refracted) as shown by the solid arrow in FIG. 32B. In this case, the position of the receiving probe 140 shown by the dashed line is a position where the eccentric distance L is zero because it is located on the transmitting sound axis plane AX1. And, as described above, even if the ultrasonic beam U is refracted, the receiving probe 120 is arranged so that the distance between the transmitting sound axis plane AX1 and the receiving sound axis AX2 is L. In the example shown in FIG. 29, the transmitting probe 110 is placed in the normal direction to the surface of the object under test E, so the eccentric distance L is as shown in FIG. 31A.

[0232] It is more preferable to set the eccentric distance L at a position where the signal strength at the defective portion D of the test object E is greater than the signal strength at the healthy portion N.

[0233] Seventh embodiment 33 is a diagram showing the configuration of an ultrasonic inspection device Z in the seventh embodiment. In the seventh embodiment, the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the inclination of the receiving probe 120. This makes it possible to increase the strength of the received signal and to increase the signal-to-noise ratio (SNR) of the signal. The installation angle adjustment unit 106 is composed of, for example, an actuator, a motor, etc., neither of which are shown in the figure.

[0234] Here, the angle θ between the transmission acoustic axis plane AX1 and the reception acoustic axis AX2 is defined as the receiving probe installation angle. In the case of FIG. 33, the transmission probe 110 is installed in the vertical direction, and therefore the transmission acoustic axis plane AX1 is in the vertical direction, and therefore the angle θ, which is the receiving probe installation angle, is the angle between the transmission acoustic axis plane AX1 (i.e., the vertical direction) and the normal line 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 acoustic axis plane AX1 exists, and sets the angle θ to a value greater than zero. That is, 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.

[0235] When the present inventors actually performed detection of a defect D with the receiving probe 120 inclined position in this manner, the signal strength of the received signal increased three times as compared to when θ=0.

[0236] Moreover, the eccentric distance L when the receiving probe 120 is disposed at an angle is defined as follows. An intersection P12 between the receiving sound axis AX2 and the probe surface of the receiving probe 120 is defined. Also, an intersection P11 between the transmitting sound axis plane AX1 and the probe surface of the transmitting probe 110 is defined. The eccentric distance L is defined as the distance between the coordinate position (x4, y4) (not shown) when the position of the intersection P11 is projected onto the xy plane, and the coordinate position (x5, y5) (not shown) when the position of the intersection P12 is projected onto the xy plane.

[0237] FIG. 34 is a diagram for explaining the reason why the seventh embodiment has an effect. The scattered wave U1 propagates in a direction deviating from the transmission sound axis plane AX1. Therefore, as shown in FIG. 34, when the scattered wave U1 reaches the outside of the test object E, it is incident on the interface between the test object E and the outside at a non-zero angle α2 with respect to the normal vector of the test object E surface. The angle of the scattered wave U1 emerging from the surface of the test object E has an angle β2, which is a non-zero exit angle, with respect to the normal direction of the test object E surface. 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 traveling direction of the scattered wave U1. In other words, the received signal strength can be increased by arranging the receiving probe 120 at an angle.

[0238] The reception effect is maximized when the angle β2 of the ultrasonic beam U emitted from the object E coincides with the angle θ between the transmission sound axis plane AX1 and the reception sound axis AX2. However, even if the angle β2 and the angle θ do not coincide completely, the effect of increasing the reception signal can be obtained, so as shown in FIG. 34, the angle β2 and the angle θ do not have to coincide completely.

[0239] Eighth embodiment 35 is a diagram showing the configuration of an ultrasonic inspection device Z in the eighth embodiment. In this embodiment, the ultrasonic inspection device Z includes an acoustic shielding member 300. The acoustic shielding member 300 shields an ultrasonic beam U traveling from the transmitting probe 110 toward the receiving probe 121. The acoustic shielding member 300 is provided on a transmission sound axis plane AX1 of the transmitting probe 110 between the subject E and the receiving probe 121.

[0240] By arranging the sound wave shielding member 300 on the transmission sound axis plane AX1, it is possible to shield the ultrasonic beam U (direct wave U3) incident on the receiving probe 140 along the transmission sound axis plane AX1 of the transmitting probe 110. In this way, it is possible to remove the direct wave U3 component from the received signal and increase the proportion of the scattered wave U1 in the received signal. As described above, the scattered wave U1 contains a lot of information about the defect D, so this embodiment can further improve the detectability of the defect D.

[0241] FIG. 36 is a plan view showing the positional relationship between the receiving probe 121 and the sound wave shielding member 300. As shown in FIG. In this embodiment, the size of the rectangular sound wave shielding member 300 is, for example, such that the width of the sound wave shielding member 300 (the length in the minor axis direction of the receiving probe 121) is set to include the transmission sound axis plane AX1 of the ultrasonic beam U and is smaller than the width of the receiving probe 121. In this embodiment, the width is, for example, 3 mm, and the length of the sound wave shielding member 300 (the length in the major axis direction of the receiving probe 121) is set to be equal to or greater than the length W2 in the major axis direction of the transmitting probe 110, but it goes without saying that the size is not limited to this. As shown in FIG. 36, the sound wave shielding member 300 is installed so as to include the transmission sound axis plane AX1. With this arrangement, the direct wave U3 of the linearly convergent beam can be effectively shielded, and only the scattered wave U1 component can be received. As a result, the interference caused by the direct wave U3 component in the received signal can be reduced, so that even the transmitting probe 110 can detect a minute defect D.

[0242] The size of the sound wave shielding member 300 can be determined, for example, by experiments, simulations, etc., depending on, for example, the beam diameter of the ultrasonic beam U, the physical properties (for example, material) of the object E, the frequency of the ultrasonic beam U, etc. In addition, by using a non-converging type probe for the receiving probe 140, more scattered wave U1 components can be received.

[0243] In this embodiment, the reception sound axis AX2 can be arranged coaxially with the transmission sound axis plane AX1, but the reception sound axis AX2 and the transmission sound axis plane AX1 may be arranged to substantially coincide (or may be arranged to completely coincide).

[0244] The material of the sound wave shielding member 300 may be any material that reduces the transmission of the ultrasonic beam U, and may be, for example, a metal (such as stainless steel) or a resin material. The sound wave shielding member 300 may be attached to the surface of the receiving probe 121.

[0245] The eighth embodiment can also use the control device 2 shown in Fig. 31. In the eighth embodiment, similarly to the sixth embodiment described with reference to Fig. 31, the direct wave U3 component is reduced by shifting the position of the receiving probe 121 from the transmitting sound axis plane AX1. Therefore, there is no need to provide a filter section. In addition, there is no need to shift the excitation frequency fex from the natural frequency of the transmitting probe 110.

[0246] Furthermore, similarly to the sixth embodiment, by making the eccentric distance L of the receiving probe 121 equal to or greater than zero and by extracting and detecting an appropriate frequency range using the filter section 240, the reduction of the direct wave U3 is reduced in both a spatial manner and a frequency manner, which is even more effective.

[0247] Ninth embodiment FIG. 37 is a diagram illustrating an ultrasonic inspection device Z according to the ninth embodiment. In this embodiment, the scanning measurement device 1 includes a point-focus type transmission probe 119 (second transmission probe) in addition to the line-focus type transmission probe 110. The transmission probe 119 emits a point-converged ultrasonic beam U toward the object to be inspected E. By including the transmission probe 110, the two-dimensional position of the defect D can be known.

[0248] In the embodiment shown in FIG. 37, the scanning measurement device 1 includes a transmitting probe 119 in addition to the embodiment in FIG. 1, and the transmitting probe 119 is attached to the transmitting probe scanning section 103. The scanning measurement device 1 includes a receiving probe 122 (second receiving probe) having a similar configuration to the receiving probe 121, and is installed on the opposite side of the transmitting probe 119 with respect to the test subject E. In the illustrated example, the receiving probe 121 is installed directly below the transmitting probe 119. The receiving probe 122 is fixed to the receiving probe scanning section 104. In this way, the transmitting probe 119 (second transmitting probe) and the receiving probe 122 scan the xy plane while maintaining their relative positions.

[0249] The transmitting probe 119 is a point-focus type transmitting probe. In this embodiment, the receiving probe 122 is a non-focus type receiving probe. In this way, if the focal length of the receiving probe 122 is longer than that of the point-focus type transmitting probe 119, the scattered wave U1 can be detected efficiently, which is more preferable for detecting a minute defect D. However, the receiving probe 122 may be a point-focus type receiving probe.

[0250] Fig. 38 is a plan view showing the positional relationship between an ultrasonic beam U emitted from a line-focus type transmitting probe 110 and an ultrasonic beam Up emitted from a point-focus type transmitting probe 119. Fig. 38 shows the beam shapes at positions corresponding to the vicinity of the focal points of the ultrasonic beams U and Up, so the ultrasonic beam U is linear and the ultrasonic beam Up is dotted. The receiving probes 140 and 121 corresponding to the transmitting probe 110 are installed on the opposite side with respect to the subject E, so the positions of the receiving probes 140 and 121 are indicated by dotted lines.

[0251] Fig. 39A is a diagram showing the defect imaging process. Fig. 39B is a diagram showing the process performed subsequent to the process shown in Fig. 39A. Fig. 39C is a diagram showing the process performed subsequent to the process shown in Fig. 39B. Figs. 39A, 39B, and 39C are used to show the defect imaging process in this embodiment. For ease of explanation, the size of the inspected object E is assumed to be 40 mm x 60 mm, and the length WL, which is the width of the major axis of the ultrasonic beam U emitted by the transmission probe 110, is assumed to be 20 mm.

[0252] First, as shown by the solid black arrow in FIG. 39A, the upper half of the object E (upper half of the paper in FIG. 39A) is scanned by the transmitting probe 110 from left to right, and then the lower half of the object E (lower half of the paper in FIG. 39A) is scanned by the transmitting probe 110 from right to left. This allows the entire object E to be inspected. At this time, a defect signal appears at the location where the defective portion D exists. The location where this defect signal is detected is called a defect detection area 2100. FIG. 39A shows a case where two defect detection areas 2101 and 2102 exist as the defect detection area 2100. When defect detection is performed using a linear convergent beam, the defect signal indicates that a defect exists somewhere within the range of the length WL, so the defect detection areas 2101 and 2102 become areas having a width of the length WL.

[0253] Next, as shown by the black solid arrow in Fig. 39B, only the defect detection areas 2101, 2102 are inspected. The inspection is performed by scanning using the point-focus type transmitting probe 119 and the non-focus type receiving probe 122. In many cases, the defect detection areas 2101, 2102 are rectangular areas extending in the long axis direction of the transmitting probe 110. For this reason, as shown by the black solid arrow in Fig. 39B, it is more preferable to scan in a direction perpendicular to the scanning axis when scanning with the transmitting probe 110 (the y-axis direction in the figure), since this allows the defect detection areas 2101, 2102 to be scanned with fewer turns.

[0254] 39C, the defect detection areas 2101, 2102 are scanned using the transmitting probe 119 and the receiving probe 122, thereby making it possible to know the xy position of the defect D in the defect detection areas 2101, 2102. The defect D is imaged using the obtained xy position of the defect D.

[0255] As described above, in the ninth embodiment, the defect detection areas 2101 and 2102 in which the line focus type transmission probe 110 is scanned to detect defect signals are scanned by the point focus type transmission probe 119 to image the defect D. This makes it possible to image the xy position of the defect D quickly and accurately.

[0256] Tenth embodiment FIG. 40 is a diagram showing the configuration of a line focus type transmission probe 110 in the tenth embodiment. The longer the length WL of the transmission probe 110 in the long axis direction, the larger the area inspected in one scan, enabling faster inspection. On the other hand, since the length WL is long, the piezoelectric conversion element provided in the transmission probe 110 becomes large. Therefore, there are cost and technical limitations on the length WL that can be created.

[0257] Therefore, in this embodiment, the line-focus type transmitting probe 110 is composed of multiple line-focus type unit probes 1101, 1102. The number of unit probes may be three or more. This makes it possible to combine multiple unit probes 1101 and extend the length WL in the longitudinal direction. The receiving probes 121, 140 are shown by dotted lines as they are positioned on the opposite side of the transmitting probe 110 (unit probe 1101) with respect to the test subject E.

[0258] The unit probe 1102 is arranged so as to be shifted in the scanning axis direction from the unit probe 1101. In other words, the unit probes 1101 and 1102 are arranged so that their respective transmission acoustic axis planes AX1 are shifted. That is, the respective transmission acoustic axis planes AX1 of the unit probes 1101 and 1102 are arranged so as to be shifted in the scanning axis direction.

[0259] Also, the unit probes 1101 and 1102 are arranged so that they overlap in the long axis direction (y axis direction in the figure). That is, parts of the transmission sound axis planes AX1 of the unit probes 1101 and 1102 overlap when viewed from the front of the transmission sound axis plane AX1 (viewed in the x direction). In other words, the amount of overlap in the long axis direction of the unit probes 1101 and 1102 is greater than zero. Therefore, during scanning by the transmission probe 110, scanning is performed so that a part of the ultrasonic beam U irradiated from the unit probe 1101 overlaps with a part of the ultrasonic beam U irradiated from the adjacent unit probe 1102. Specifically, for example, an end of the first ultrasonic beam U overlaps with an end of the second ultrasonic beam U adjacent to the first ultrasonic beam U on the first ultrasonic beam U side. The first ultrasonic beam U is emitted from the unit probe 1101, and the second ultrasonic beam U is emitted from the unit probe 1102.

[0260] 40, the transmission acoustic axis planes AX1 overlap each other so that the overlap length Lov between the unit probes 1101 and 1102 is a positive value. In this way, by making the overlap amount in the long axis direction of the unit probes 1101 and 1102 larger than zero, the ultrasonic beam U is reliably irradiated even in the region between the two adjacent unit probes 1101 and 1102, and it is possible to eliminate any missed inspection points, which is preferable.

[0261] The positions of the receiving probes 121, 140 are similar to those of the unit probes 1101, 1102. Therefore, the positions of the receiving probes 121, 140 are arranged in Fig. 40 so that the receiving sound axis AX2 is shifted from the transmitting sound axis plane AX1. By doing so, the direct wave U3 component of the ultrasonic beam emitted from the unit probes 1101, 1102 does not enter the receiving probes 121, 140, so that it becomes easier to detect the scattered wave U1 at the defect D, and it becomes possible to detect a minute defect D.

[0262] In order to prevent the direct wave U3 component from being incident on the receiving probes 121, 140, the transmitting sound axis plane AX1 is arranged not to intersect with the receiving surfaces of the receiving probes 121, 140. For this reason, as shown in Fig. 40, the two receiving probes 121, 140 are arranged on opposite sides of each other in the scanning axis direction with respect to the unit probes 1101, 1102.

[0263] 40 shows a configuration in which the direct wave U3 component is reduced by shifting the transmission sound axis plane AX1 and the reception sound axis AX2. Alternatively, as shown in the first embodiment, the direct wave U3 component can also be reduced by shifting the excitation frequency fex from the natural frequency of the unit probes 1101 and 1102 and setting the reception signal to an appropriate frequency range using the filter section 240. In this case, it is not necessarily necessary to displace the transmission sound axis plane AX1 and the reception sound axis AX2.

[0264] (Drive sequence) In the tenth embodiment, it is possible to use the control device 2 having the configuration in Fig. 10 above. However, the signal amplifier 212 has two output terminals, each of which is connected to the unit probes 1101 and 1102. The signal amplifier 222 in the receiving system 220 also has two input terminals, each of which is connected to the unit probes 1101 and 1102.

[0265] 41 is a timing diagram showing a drive sequence in a configuration using two unit probes 1101, 1102. The horizontal axis of the diagram indicates elapsed time. The vertical items TR-1 and TR2 indicate the drive sequences of the unit probes 1101, 1102, respectively. The vertical items RC-1 and RC-2 indicate the reception timing sequences of the receiving probes 140, 121 installed below the unit probes 1101, 1102, respectively.

[0266] In the figure, the hatched parts shown in the waveforms (TR-1, TR-2) of the unit probes 1101, 1102 indicate the wave packets of the burst wave voltages applied to the respective unit probes 1101, 1102. The repetition period Tr of the wave packets is preferably 0.5 ms to 10 ms, and is set to 5 ms in this embodiment.

[0267] The hatched areas in the timing charts (RC-1, RC2) of the receiving probes 140, 121 represent the receiving period. The receiving period is the period during which the signal of the ultrasonic beam U incident on the receiving probes 140, 121 is acquired. The receiving period is typically set to 0.1 ms to 2 ms after the wave packet of the corresponding unit probes 1101, 1102 ends. In this embodiment, the receiving period is set to 0.5 ms. The length of the receiving period is mainly determined by the time required for the ultrasonic beam U to reach the distance from the unit probes 1101, 1102 to the receiving probes 140, 121. For this reason, the suitable length of the receiving period changes depending on the material of the fluid F, the installation positions of the unit probes 1101, 1102 and the receiving probes 140, 121, etc.

[0268] 41, the ultrasonic beam U is emitted at the same time by all of the unit probes 1101, 1102, and the ultrasonic beam U is received at the same time by all of the receiving probes 140, 121. In this manner, scanning can be speeded up and inspection can be performed in a short time not only when the number of unit probes is small, for example, two or less, but also when the number of unit probes is large, for example, three or more.

[0269] 42 is a timing diagram showing a driving sequence in another embodiment related to the tenth embodiment. In this example, inside the signal amplifier 212, one signal amplifier circuit is electronically switched by a switch such as a relay, and two signals are output. The signal amplifier 222 of the receiving system 220 also has one signal amplifier circuit and an electronic switch inside the signal amplifier 222, and two input signals are processed.

[0270] As shown in Fig. 42, after a wave packet of a burst wave is applied to a unit probe 1101 (TR-1), a receiving period is set to the corresponding receiving probes 140, 121 (RC-1). Next, a wave packet is applied to a unit probe 1102 (TR-2), and then a receiving period is set to the corresponding receiving probes 140, 121 (RC-2). The delay time Td between the wave packet of TR-1 and the wave packet of TR-2 is typically 0.2 ms to 2 ms.

[0271] 42, first, an ultrasonic beam U is emitted and received using a pair of unit probes 1101 and receiving probes 140. Then, after at least the ultrasonic beam U is emitted, an ultrasonic beam U is emitted and received using another pair of unit probes 1102 and receiving probes 140. The ultrasonic beam U may be emitted from the other pair of unit probes 1102 before or after the ultrasonic beam U is received by the pair of unit probes 1101 and receiving probes 140.

[0272] By using this driving sequence, two transmission outputs are not performed simultaneously, so that an electronic switch can be used. The same applies to the receiving circuit. This configuration has the advantage that the transmitting circuit and receiving circuit can be constructed inexpensively.

[0273] Eleventh embodiment FIG. 43 is a functional block diagram of the control device 2 in the eleventh embodiment.

[0274] (Accumulation of frequency component data) The data processing unit 201 includes a storage unit 261, an imaging unit 262, and a display unit 263. The storage unit 261 includes a database 261a. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, the database 261a, and a display unit 263.

[0275] In the example of the present disclosure, the control device 2 includes a database 261a in a storage unit 261 constituting the data processing unit 201. The database 261a associates information that affects the detection accuracy of the defective part D in the object E to be inspected (hereinafter, referred to as "information on the object E to be inspected") with frequency parameters. The information here includes, for example, the inspection conditions of the object E to be inspected. Depending on the inspection conditions, the appropriate frequency parameters may differ. The appropriate frequency parameters here are frequency parameters for increasing the difference between the frequency spectrum of the healthy part N and the frequency spectrum of the defective part D to a level that makes the defective part D detectable. The frequency parameters indicate a frequency set {ωn} suitable for detecting the defective part D. Therefore, a user can specify a part of the frequency spectrum used to create an image 273 (described later) by inputting the inspection conditions into an input unit 272 (described later).

[0276] In this embodiment, it is more preferable to add the excitation frequency fex used to the frequency parameters and store it in the database 261a. The detection performance of the defect D changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmission probe 110. Therefore, by registering the excitation frequency fex (the amount of shift) in the database 261a, it becomes possible to select an appropriate excitation frequency fex for the next and subsequent measurements.

[0277] When registering the used excitation frequency fex as a frequency parameter, since the shift amount from the natural frequency fres is important, it is preferable to register it in the form of the difference amount Δfex=fex-fres. Furthermore, it is preferable to register the ratio of the difference amount Δfex to the natural frequency fres (Δfex / fres).

[0278] The inspection conditions include, for example, at least one of the following: the material of the object E to be inspected, the thickness of the object E to be inspected, the structure of the object E to be inspected (e.g., whether it is a single-layer structure or a multi-layer structure), the position of the object E to the receiving probe 121 and the transmitting probe 110 (e.g., the position in the z direction), and the type of fluid F. Since these are pieces of information that can affect the appropriate frequency parameters, the appropriate frequency parameters can be determined by the user inputting at least one of these pieces of information.

[0279] FIG. 44A is an example of the database 261a. In the example of the present disclosure, the frequency parameters are a set of ratios f / f0 relative to the transmission frequency f0 (FIG. 14). In the example shown in FIG. 44A, the preferred frequency parameters for information on the object E are expressed as a certain range. The information here is, for example, the thickness and material of the object E, as an example for explanation. When measurements are performed with the ultrasonic inspection device Z shown in FIG. 1 and the preferred frequency parameters are repeatedly registered, i.e., updated, the information is accumulated in the database 261a.

[0280] Fig. 44B is a three-dimensional diagram showing the database 261a shown in Fig. 44A. The information on the inspected object E is multidimensional information having multiple axes. That is, when the information on the inspected object E is divided into components It[k] (k is an integer equal to or greater than 1) and expressed, k=1, 2, ... corresponds to each axis of the multidimensional information. In the example shown in Fig. 44B, as an example for explanation, It[1] is the thickness of the inspected object E, and It[2] is the material of the inspected object E.

[0281] In Fig. 44A, information related to the inspected object E, which is multidimensional information, is abstracted and shown as one axis. Specifically, as shown in Fig. 44B, the information related to the inspected object E is composed of multiple axes. Therefore, in the example of the present disclosure, the database 261a is a database that has the inspected object information, which is multidimensional information, as an axis.

[0282] The database 261a may be expressed in a tabular format. That is, a table may be created in which suitable frequency parameters are recorded as one record (row) for each piece of information related to the multidimensional test subject E. When the database 261a is processed by a computer or the like, it may be expressed in a tabular database format, or in a database format in which each piece of information related to the multidimensional test subject E is represented as one record.

[0283] (Frequency Selection) FIG. 45 is a diagram showing a schematic configuration example of an operation screen 270 of the ultrasonic inspection device Z in the example of the present disclosure. The operation screen 270 is displayed on the display device 3 (FIG. 43) by the display unit 263 (FIG. 43). The display unit 263 displays, on the display device 3, a frequency spectrum 271 corresponding to the frequency components converted by the frequency conversion unit 230 (FIG. 43) as described above, and an input unit 272 that accepts input of frequency parameters by the user. In the example of the present disclosure, the display unit 263 displays the operation screen 270 of the ultrasonic inspection device Z on the display device 3, and also displays the frequency spectrum 271 and the input unit 272 on the operation screen 270. This allows the user to operate the input unit 272 while checking the operation screen 270 including the frequency spectrum 271.

[0284] In the example shown in FIG. 45, an image 273 showing the position of the defective part D of the inspected object E is displayed on the left side. A frequency spectrum 271 is displayed on the upper right side. Here, it is preferable to display the frequency spectrum 271 at a plurality of locations according to the inspection position, since comparison can be made. In particular, the frequency spectrum 271 includes a first frequency spectrum shown by a dashed line and a second frequency spectrum shown by a solid line. The dashed and solid line graphs are the dashed and solid line graphs in FIG. 12 and the like. This allows the user to compare the frequency spectra with each other, and allows the user to input the appropriate frequency components. However, the frequency spectrum 271 displayed may be only one of the first frequency spectrum or the second frequency spectrum. If the user has some experience, he or she may be able to determine the appropriate frequency parameters based on only one of the frequency parameters.

[0285] The input unit 272 is a unit into which a frequency parameter is input by a user. In the example of the present disclosure, the input unit 272 is a frequency selection unit configured with a slide bar whose length and position are adjustable. The user can input a frequency range (frequency set) for extracting signal features by adjusting the length and position of the slide bar using, for example, a mouse, a keyboard, etc., to a position corresponding to the frequency position of the frequency spectrum. The frequency range input here is the frequency parameter. After input, the frequency spectrum 271 is updated by pressing an update button 274.

[0286] Although it is preferable that the frequency spectrum 271 is displayed, it does not have to be displayed. In the case where it is not displayed, for example, the imaging unit 262 determines, as an initial frequency parameter, a frequency parameter corresponding to information on the object E received through the input unit 275 from the database 261a (FIG. 43). The input unit 275 receives information that affects the detection accuracy of the defect part D in the object E (the above-mentioned "information on the object E"). The display unit 263 displays the input unit 275 on the display device 3. If there is no corresponding frequency parameter, a frequency parameter corresponding to information closest to that information is determined. The determined frequency parameter is displayed on the display device 3. The imaging unit 262 creates an image 273 (FIG. 45. defect image) based on the determined frequency parameter. Examples of the image 273 include the above-mentioned first defect image and second defect image. By using the information in the database 261a, the detection accuracy of the defect part D can be improved.

[0287] Twelfth embodiment 46 is a functional block diagram of an ultrasonic inspection device Z according to the twelfth embodiment. This embodiment does not necessarily need to include the input unit 275 (FIG. 45).

[0288] The signal processing unit 250 includes an update unit 291 (frequency parameter update unit). The update unit 291 automatically updates the frequency parameters. An example of a more specific process in the update unit 291 will be described. The imaging unit 262 calculates the above-mentioned signal feature amount while changing the frequency parameters for the received signals of two points, the defective part D and the healthy part N. Then, the update unit 291 searches for and determines the frequency parameters that maximize the difference in the signal feature amount between the defective part D and the healthy part N, for example (not limited to the maximum, and may be large enough to detect the defective part D). Using the frequency parameters thus updated by the update unit 291, the imaging unit 262 creates the image 273. The frequency parameters thus updated are also registered in the database 261a, and the database 261a is updated.

[0289] It is more preferable to add the excitation frequency fex used to the frequency parameters and store them in the database 261a. Therefore, it is preferable that the database 261a includes information on the excitation frequency fex. Since the detectability of the defect D changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmission probe, by registering this in the database 261a as well, it becomes possible to select an appropriate excitation frequency fex for the next and subsequent measurements.

[0290] When registering the used excitation frequency fex as a frequency parameter, since the shift amount from the natural frequency fres is important, it is preferable to register it in the form of the difference amount Δfex=fex-fres. Furthermore, it is preferable to register the ratio of the difference amount Δfex to the natural frequency fres (Δfex / fres).

[0291] The determined frequency parameters may be displayed on the display device 3. Instead of automatically updating the frequency parameters by the update unit 291, the user may specify the frequency parameters through the input unit 272 while viewing the image 273. This also makes it possible to further improve the detection accuracy of the defective portion D.

[0292] Thirteenth embodiment 47 is a diagram showing the configuration of an ultrasonic inspection device Z of a thirteenth embodiment. In the thirteenth 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 via the liquid W, which is the fluid F. The object E to be inspected is placed below the liquid level L0 of the liquid W and is immersed in the liquid W.

[0293] As in the first embodiment, in this embodiment, the excitation frequency fex is set to a frequency 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 shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, it is possible to improve the performance of the ultrasonic inspection device Z of this embodiment.

[0294] 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, a more preferable effect is obtained as described above.

[0295] 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 effect of the present disclosure is even greater. Thus, when gas G is used as the fluid F, the present disclosure can achieve a more preferable effect.

[0296] FIG. 48 is a diagram showing the hardware configuration of the control device 2. The above-mentioned configurations, functions, and each part constituting the block diagram may be realized by hardware, for example, by designing a part or all of them as an integrated circuit. Also, as shown in FIG. 48, the above-mentioned configurations, functions, and the like may be realized by software, by a processor such as a CPU 252 interpreting and executing a program that realizes each function. The control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (SSD, HDD, etc.), a communication device 254, and an I / F 255. Information such as a program, table, and file that realizes each function can be stored in a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).

[0297] Fig. 49 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 ultrasonic inspection device Z, and will be described as an example with reference to Figs. 1 and 10 as appropriate. The ultrasonic inspection method of the present disclosure inspects an object E to be inspected (Fig. 1) by irradiating an ultrasonic beam U onto the object E to be inspected (Fig. 1) via a gas G (Fig. 1, an example of a fluid F). Note that, although this ultrasonic inspection method will be described for an embodiment in which gas G is used as the fluid F, it goes without saying that this ultrasonic inspection method is also effective for an embodiment in which liquid W is used as the fluid F.

[0298] The ultrasonic inspection method of the present disclosure includes steps S101 to S105, S111, and S112. First, in response to a command from the control device 2, the line focus type transmission probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmission probe 110.

[0299] In step S101, the transmitting probe 110 is excited at an excitation frequency fex that is higher than the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110, and an ultrasonic beam U is emitted.

[0300] Next, in step S102 (reception step), the receiving probe 121 receives the ultrasonic beam U.

[0301] Thereafter, the filter unit 240 performs step S103 (filter processing step) of reducing components (maximum intensity frequency components) in a specific frequency range, specifically, a frequency range including the maximum component frequency fm, based on the signal (e.g., waveform signal) of the ultrasonic beam U received by the receiving probe 121. That is, in step S103, the maximum intensity frequency component of the signal of the ultrasonic beam U received in step S102 is reduced.

[0302] 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 filtered signal and generating signal intensity data (calculating the signal intensity). Therefore, in step S104, the base component W3 of the fundamental wave band W1 in the signal of the ultrasonic beam U is detected. In this embodiment, a peak-to-peak signal is used as a method of generating signal intensity data. This is the difference between the maximum and minimum values ​​of the signal.

[0303] 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 manner, the signal intensity data is visualized. This is step S105.

[0304] Note that Figure 12 above shows the case where the scanning position information is one-dimensional (one direction). In the case where the scanning position information is two-dimensional in x and y, the signal intensity data is plotted to show the defect area D as a two-dimensional image, which is then displayed on the display device 3.

[0305] 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 process. 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 process returns to step S101.

[0306] According to the ultrasonic inspection device Z and ultrasonic inspection method described above, the inspection time required to detect the defect D can be significantly reduced, and the detection performance of the defect D, for example the performance of detecting a minute defect, can be improved.

[0307] In each of the above embodiments, an example is described in which the defect D is a cavity, but the defect D may be a foreign object containing a material different from the material of the object E to be inspected. In this case, too, a difference (Gap) in acoustic impedance occurs at the interface where the different materials come into contact, causing 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.

[0308] The present disclosure is not limited to the above-described embodiments, and includes various modified examples. 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 configurations described. In addition, it is possible to replace a 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. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0309] In each embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all of the control lines and information lines in the product are shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0310] 1. Scanning measurement device 100 Sending Probes 105 Distance adjustment section 106 Installation angle adjustment section 110 Sending Probes 1100 Virtual Element 1101 Unit Probe 1102 Unit Probe 119 Sending Probes 120 Received Probes 121 Received Probes 122 Incoming Probes 130 long axis 131 Scanning Axis 140 Received Probes 2. Control device 201 Data Processing Unit 202 Drive unit 203 Position measurement unit 204 Scan Controller 210 Transmission System 2100 Defect detection area 2101 Defect detection area 2102 Defect detection area 211 Waveform Generator 212 Signal Amplifier 213 Transmission frequency setting unit 220 Receiving System 222 Signal Amplifier 223 Display section 224 Reception Department 230 Frequency conversion unit 231 Signal strength calculation unit 240 Filter section 241 Frequency Component Conversion Unit 242 Frequency Selection Unit 243 Frequency component inverse transform unit 244 Detector 245 Decision Section 250 Signal Processing Section 261a Database 262 Imaging Department 263 Display section 270 Operation screen 271 Frequency Spectrum 272 Input section 273 images 274 Update button 275 Input section 291 Update Department 3 Display device 300 Sound wave shielding material 4 Input Devices AX Transmission Axis AX1 Transmission sound axis surface AX2 Receiving Sound Axis AX3 transmission axis D Defective part E. Test object S sweep area U Ultrasonic beam W1 Fundamental wave band W2 Frequency Range W3 Foothills

Claims

1. 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, comprising: a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam, and a control device that controls driving of the scanning and measuring device, The scanning measurement device is a line-focus type transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is disposed on the opposite side of the transmitting probe with respect to the object to be inspected, The transmitting probe emits an ultrasonic beam when a voltage waveform of a repeating wave packet composed of a wave packet having a wave number of two or more is applied to the transmitting probe; Driving the transmitting probe at an excitation frequency higher than a resonant frequency of the transmitting probe; The control device includes a signal processor. The signal processing unit includes a filter unit that reduces at least a maximum intensity frequency component of the reception signal of the receiving probe, The filter unit detects frequency components other than the maximum intensity frequency component in a fundamental wave band that includes the maximum intensity frequency component.

2. 2. The ultrasonic inspection device according to claim 1, wherein an angle between a long axis, which is the axis of the longest part of the convergence portion of the ultrasonic beam emitted from the transmitting probe, and a scanning axis, which is the scanning direction of the transmitting probe, is greater than or equal to 60° and less than 120° with respect to the scanning direction.

3. 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.

4. 2. The ultrasonic inspection apparatus according to claim 1, wherein the receiving probe is a non-focused receiving probe.

5. 2. The ultrasonic inspection device according to claim 1, wherein a full width at half maximum of the frequency spectrum of the fundamental wave band is 50% or less of a maximum component frequency, which is a frequency corresponding to the maximum intensity frequency component.

6. The filter unit includes: a frequency component converter for converting a received signal of the receiving probe into frequency components; a frequency selection unit that selects the base component by removing a frequency band including the maximum intensity frequency component; 2. The ultrasonic inspection apparatus according to claim 1, further comprising:

7. 2. The ultrasonic inspection apparatus according to claim 1, wherein the excitation frequency is set within a frequency range of the fundamental wave band.

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

9. 2. The ultrasonic inspection device according to claim 1, wherein an absolute value of a difference between the excitation frequency and the resonant frequency is 25% or less of a maximum component frequency, which is a frequency corresponding to the maximum intensity frequency component.

10. 2. The ultrasonic inspection device according to claim 1, wherein an absolute value of a difference between the excitation frequency and the resonant frequency is 15% or less of a maximum component frequency, which is a frequency corresponding to the maximum intensity frequency component.

11. 2. The ultrasonic inspection device according to claim 1, wherein the frequencies detected by the filter unit include frequencies in a range of (fm±0.25 fm), where fm is a maximum component frequency that is a frequency corresponding to the maximum intensity frequency component.

12. 2. The ultrasonic inspection apparatus according to claim 1, wherein the scanning measurement device includes a point-focus type transmitting probe that emits the ultrasonic beam.

13. 13. The ultrasonic inspection device according to claim 12, wherein a defect detection area in which a defect signal is detected by scanning the line focus type transmission probe is scanned by the point focus type transmission probe to image the defect portion.

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

15. 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, comprising: a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam, and a control device that controls driving of the scanning and measuring device, The scanning measurement device is a line-focus type transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is disposed on the opposite side of the transmitting probe with respect to the object to be inspected, An ultrasonic inspection device comprising a distance adjustment unit that adjusts the eccentricity distance between the transmission sound axis plane of the transmission probe and the reception sound axis of the reception probe to a distance greater than zero.

16. 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, comprising: a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam, and a control device that controls driving of the scanning and measuring device, The scanning measurement device is a line-focus type transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is disposed on the opposite side of the transmitting probe with respect to the object to be inspected, An ultrasonic inspection device comprising: an acoustic shielding member for shielding an ultrasonic beam traveling from the transmitting probe to the receiving probe, the acoustic shielding member being disposed on a transmission acoustic axis plane of the transmitting probe between the object under inspection and the receiving probe.

17. 2. The ultrasonic inspection apparatus according to claim 1, wherein a distance between a transmission acoustic axis plane of the transmitting probe and a reception acoustic axis of the receiving probe is greater than zero.

18. the line-focus type transmission probe is composed of a plurality of line-focus type unit probes, The transmission acoustic axis planes of the unit probes are arranged to be shifted in the scanning axis direction, 16. The ultrasonic inspection device according to claim 1, wherein parts of the transmission acoustic axis planes of the unit probes overlap each other when viewed from the front.

19. 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 exciting the transmission probe at an excitation frequency higher than a resonant frequency of the line focus type transmission probe to emit an ultrasonic beam; a receiving step of receiving the ultrasonic beam; a filtering step of reducing a maximum intensity frequency component of the signal of the ultrasonic beam received in the receiving step; and detecting a signal intensity of the ultrasonic beam signal.

1. An ultrasonic inspection method comprising:

Images