JP2014074726A - Ultrasonic wave imaging method and ultrasonic wave imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a detection resolution of an internal defect in a flaw detection using a converging type ultrasonic probe with a large area of entire ultrasonic vibrator array row and a short focal distance and aperture synthesis settings.SOLUTION: The ultrasonic wave imaging method includes: a transmission and reception step in which an ultrasonic is transmitted to an object to be inspected and a reflected wave from an internal defect of the object to be inspected is received while causing a focal point which is formed by performing an aperture synthesis processing on a signal received by an array type ultrasonic probe to scan relative to the object to be inspected through water interposed between the array type ultrasonic probe and the object to be inspected; a signal processing step in which the aperture synthesis processing is made on the signals received by vibrators on the array type ultrasonic probe; a signal generation step in which the obtained aperture synthesis waveform is delayed by a preset delay time and added to generate a signal; and a display step to display the generated signal. The delay propagation time is set based on a variation in the propagation time which is obtained by calculating the propagation time based on the aperture synthesis waveform and calculating a variation in propagation time with respect to a relative position between an aperture synthesis processing made on focal point of the received signals from the respective vibrators and the preset internal defect.

Description

  The present invention relates to an ultrasonic imaging method and an ultrasonic imaging apparatus, and in particular, various shapes such as plates, tubes, and cylinders made of metal, resin, and the like using an ultrasonic flaw detection method which is a kind of non-destructive inspection method. The present invention relates to visualization of internal defects present in a subject.

  Conventionally, the ultrasonic flaw detection method, which is a kind of non-destructive inspection method, has been widely used for flaw detection of internal defects such as steel. In this internal defect inspection, in order to obtain more detailed information on internal defects, high resolution of ultrasonic images is required. There is also a demand for faster ultrasonic flaw detection. As methods for achieving both high resolution of ultrasonic images and high speed ultrasonic flaw detection, there are the following conventional techniques.

(1) Aperture synthesis method using an array type ultrasonic probe There is an aperture synthesis method as a technique aiming at high-resolution imaging (for example, refer to Patent Document 1 and Patent Document 2). The principle of the aperture synthesis method will be described by taking as an example the case of performing defect imaging by bringing the transducer array 120 shown in FIG. 23 into contact with the surface of the subject 110. An ultrasonic wave is transmitted from each transducer of the transducer array 120 to detect a defect echo, and the beam path of the defective echo in the subject 110 is measured from the time from the transmission of the ultrasonic wave to the reception of the echo. Since the ultrasonic waves transmitted and received from the individual transducers 120p (p = 1, 2,...) Have a spatial spread, the beam path of the echo detected by the transducer 120p is Wp (p = 1, 2,..., Of the hollow sphere Sp (p = 1, 2,...) Having a radius Wp, a reflection source somewhere in the directivity angle range of the ultrasonic wave transmitted and received by the transducer 120p. Exists. When echoes are detected using all the transducers and the intersection of the hollow spheres Sp is obtained, this intersection becomes a defect image. In the example of FIG. 23, a defect image is synthesized from the beam path of echoes detected by A, B, C, D, and E in the transducer array 120.

  In the aperture synthesis method using an array-type ultrasonic probe, it is possible to synthesize a defect image in a certain area corresponding to the arrangement and shape of the array transducer, and there is no need for mechanical scanning of the ultrasonic probe. Ultrasonic flaw detection can be performed. Then, if a focus is set at a certain depth position and aperture synthesis processing is performed, flaw detection equivalent to a focused beam is possible.

(2) Application of defect imaging processing method using focused beam There is also a method of performing defect imaging processing in combination with a focused beam (see, for example, Patent Document 3). In this method, as shown in FIG. 23, the reconstructed image of the subject is divided into minute elements of the same size _, and becomes a defect echo source from the beam path distance W _{i, j} measured at each measurement point P _{i, j.} This is a method characterized by selecting possible microelements PF _{k, l, m} , and this method can improve resolution in flaw detection using a focused beam. If the waveform obtained by setting the focus at a certain position and performing aperture synthesis in (1) above is equivalent to the waveform obtained by flaw detection using a focused beam, an array type ultrasonic probe was used. Can be combined with aperture synthesis.

JP-A-8-62191 JP 2000-65808 A JP 2004-150875 A

Edited by Japan Nondestructive Inspection Association, “Ultrasonic Flaw Test II”, Japan Nondestructive Inspection Association (2000), p. 151-152

  However, even when the above (1) and (2) are combined, there is a problem that the resolution is not improved when a highly focused line-focusing linear array type ultrasonic probe is used. The reason is shown below.

  In the method (2), it is assumed that transmission / reception of ultrasonic waves is performed at a single point of the center of the ultrasonic transducer, and the round-trip propagation time from the ultrasonic probe to the microelement is as shown in FIG. The calculation is based on the assumption that ultrasonic waves propagate on the only path from the transmission / reception point to the minute element. However, actually, transmission / reception of ultrasonic waves is performed by an array row of a plurality of ultrasonic transducers. For this reason, in particular, when using the aperture synthesis setting in which the area of the array of ultrasonic transducers used for aperture synthesis processing is large and the focal length is short, it is far from the assumption of transmission / reception at a single point. It has been difficult to increase the resolution of internal defect imaging with the technique described in the above.

  The present invention has been made in view of such circumstances, and imaging of internal defects in flaw detection using an aperture synthesis setting in which the area of an ultrasonic transducer array array used for aperture synthesis processing is large and the focal length is short. It is an object of the present invention to provide an ultrasonic imaging method for internal defects and an ultrasonic imaging apparatus for internal defects that can improve the resolution.

An ultrasonic imaging method for an internal defect according to the present invention includes:
The focus formed by interposing water between the array-type ultrasonic probe and the subject and subjecting the reception signal of the array-type ultrasonic probe to aperture synthesis is scanned relative to the subject. While transmitting and receiving an ultrasonic wave toward the subject and receiving a reflected wave from an internal defect of the subject;
A signal processing step of performing aperture synthesis processing on the signal received by each transducer of the array-type ultrasonic probe;
A signal generation step of generating a signal by adding the resultant aperture synthesized waveform after being delayed by a set delay time; and
An ultrasonic imaging method of an internal defect comprising a display step of displaying the generated signal,
The delay time is
By calculating the propagation time based on the aperture synthesis waveform, the amount of change in the propagation time with respect to the relative position between the focus of the aperture synthesis processing performed on the received signal of each transducer of the array-type ultrasonic probe and the set internal defect is obtained. , The amount of change in the propagation time is set.

An ultrasonic imaging method for an internal defect according to the present invention includes:
The amount of change in the propagation time is determined by dividing each transducer into a plurality of regions, obtaining a waveform of a reflected wave from a set internal defect received by each divided region, and synthesizing the waveform for each transducer. Then, it is calculated by using the signal of each vibrator.

An ultrasonic imaging method for an internal defect according to the present invention includes:
When dividing the plurality of regions of each vibrator,
Calculate the propagation path of ultrasonic waves in multiple directions from the set internal defect,
Calculate the intersection of the path and the ultrasound probe,
Using the obtained intersection point, the ultrasonic probe surface is divided into a plurality of areas with the obtained intersection point as a representative point, and each divided ultrasonic probe area and the set internal defect corresponding to each divided area, Is propagated through the propagation path traced when calculating the intersection of the ultrasonic wave propagation path and the ultrasonic probe.

An ultrasonic imaging method for an internal defect according to the present invention includes:
When obtaining the waveform of the reflected wave from the set internal defect received by each divided region of each vibrator,
Calculate the propagation path of ultrasonic waves in multiple directions from the set internal defect,
Calculate the intersection of the path and the ultrasound probe,
It is assumed that the propagation of ultrasonic waves between the obtained intersection and the set internal defect corresponding to each divided area propagates through the propagation path traced when calculating the intersection of the ultrasonic propagation path and the ultrasonic probe. Calculate
The ultrasonic wave propagation waveform between each divided area of each transducer and the set internal defect is interpolated or extrapolated from the ultrasonic wave propagation waveform between the intersection near each area and the set internal defect. To calculate.

The ultrasonic imaging apparatus for internal defects according to the present invention is as follows.
The focus formed by interposing water between the array-type ultrasonic probe and the subject and subjecting the reception signal of the array-type ultrasonic probe to aperture synthesis is scanned relative to the subject. While transmitting and receiving ultrasonic waves toward the subject, and receiving reflected waves from internal defects of the subject;
Signal processing means for performing aperture synthesis processing on a signal received by each transducer of the array-type ultrasonic probe;
A signal generating means for generating a signal by delaying the obtained aperture synthetic waveform by the set delay time data and adding the signal;
An ultrasonic imaging method of an internal defect comprising display means for outputting and displaying the generated signal data in an image memory,
The delay time data is
The propagation time is calculated based on the synthetic aperture waveform, and is calculated from the amount of change in the propagation time with respect to the relative position between the focal point of the synthetic aperture processing performed on each transducer signal of the array-type ultrasonic probe and the set internal defect. , The amount of change in the propagation time is set.

  In the present invention, as described above, the propagation time of the ultrasonic wave propagating between the array-type ultrasonic probe and a defect set at a predetermined position inside the subject (set internal defect) is set as the array-type ultrasonic probe. The entire transmission / reception surface of each transducer of the acoustic probe is divided into a plurality of regions, an ultrasonic waveform transmitted / received between each of the divided regions and the set internal defect is obtained, and the waveform is obtained as the array type ultrasonic wave. The entire surface of each transducer of the probe is synthesized, and the signal of each synthesized transducer is calculated from the signal waveform obtained by aperture synthesis, so that the focus and setting inside the array type ultrasonic probe formed by aperture synthesis or focusing Obtain the amount of change in the propagation time relative to the position relative to the defect, obtain the data of the equal propagation time plane or delay time group based on the amount of change in the propagation time, and generate the defect image using the data Has manner, Therefore, in flaw detection using a set of the total area of the ultrasound transducer array column is large focal length shorter probe and aperture synthesis, it is possible to improve the resolution of imaging by the signal processing.

It is a block diagram of the imaging device of the internal defect by the ultrasonic wave which concerns on Embodiment 1 of this invention. It is explanatory drawing of the equal propagation time surface of this invention. It is the flowchart which showed the processing method for obtaining ultrasonic propagation time by ultrasonic propagation analysis. It is the flowchart which showed the processing method for acquiring the ultrasonic waveform in a defect position. It is the flowchart which showed the processing method for receiving with an array type ultrasonic probe and performing an aperture synthesis process and acquiring an output waveform. It is explanatory drawing which showed the procedure of the method of obtaining propagation time. It is the flowchart which showed the processing method at the time of preparing an equal propagation time surface. It is explanatory drawing which showed the relationship between the variation | change_quantity of propagation time, and an equal propagation time surface. It is an example of the data of an equal propagation time surface. It is the flowchart which showed the process at the time of synthesize | combining a defect image. It is explanatory drawing of water propagation time and to-be-inspected object propagation time. It is explanatory drawing of the method of drawing the equal propagation time surface in a different propagation time using one equal propagation time surface. It is explanatory drawing of an imaging process. It is the figure which showed the effect of the Example of this invention in contrast with the result of the conventional method. In Embodiment 2 of this invention, it is explanatory drawing of the method of comprising a delay time from the profile of propagation time variation | change_quantity, and performing a waveform resynthesis. It is a flowchart of the method of obtaining ultrasonic propagation time in Embodiment 3 of this invention. It is explanatory drawing of the method of obtaining the point on an array probe. It is explanatory drawing of the method of obtaining a micro area from a probe set point. It is a flowchart of ultrasonic waveform acquisition at a defect position. It is the flowchart of the output waveform income which received with the array probe and performed the aperture synthetic | combination process. It is a flowchart of the method of obtaining ultrasonic propagation time in Embodiment 4 of this invention. It is a flowchart of the method of obtaining the propagation time and attenuation | damping of a micro area representative point from the propagation time and attenuation | damping of a probe set point. It is principle explanatory drawing of the conventional opening synthetic | combination method. It is the figure which showed the line focusing type linear array type ultrasonic probe. It is explanatory drawing of the defect image synthesis method in a prior art (patent document 3). It is explanatory drawing which shows the path | route of the ultrasonic probe and microelement in a prior art. It is the figure which showed the comparison (prior art example and Embodiment 3) of the propagation path determination method.

  The present invention pays attention to the fact that ultrasonic transmission / reception is performed by an array row of a plurality of transducers in an array type ultrasonic probe, and the position of a focal point and internal defects formed by aperture synthesis or focusing by the array type ultrasonic probe. By analyzing in advance how the propagation time of the reflected wave from the internal defect changes depending on the position, and performing signal processing using the analysis result, the area of the entire ultrasonic transducer array row can be reduced. This is based on the finding that it is possible to improve the resolution of flaw detection using a probe with a large focal length and a short aperture. Specific examples thereof will be described as Embodiments 1 to 4, respectively.

Embodiment 1. FIG.
FIG. 1 is a block diagram showing a configuration of an ultrasonic imaging apparatus according to Embodiment 1 of the present invention.
In FIG. 1, reference numeral 1 denotes a subject to be examined. In this example, the subject 1 is a stationary subject, water is used as a medium, and an internal defect is imaged using an immersion method. Reference numeral 10 denotes an array-type ultrasonic probe that transmits and receives ultrasonic waves, and an ultrasonic beam is transmitted from the transmission circuit 11 to the subject 1 by an electric signal that is transmitted to each transducer through a drive element selection circuit 12 through a drive element selection circuit 12. And a reflected wave (echo) from the surface and inside of the subject 1 is received. The received signal is subjected to aperture synthesis processing by the receiving circuit 13 and the array signal processing circuit 14 and is amplified to an appropriate level convenient for later signal processing. The array-type ultrasonic probe 10 is two-dimensionally scanned (xy scanning) or one-dimensionally scanned (y-scanned) on the subject 1 by appropriate scanning means, and the position thereof is the x-direction position detecting means 21 and the y-direction position. Each is detected by the detection means 22 and sent to the output waveform data section 15.

The output waveform data section 15 is based on the outputs of the array signal processing circuit 14, the x-direction position detection means 21 and the y-direction position detection means 22, and the focal points P _i, Output waveform data corresponding to _j (i: position in the x direction, j: position in the y direction) is detected, and the output is sent to the defect image composition processing unit 16. The defect image composition processing unit 16 measures the difference between the transmission time and the reception time of the defect echo 52, that is, the ultrasonic propagation time. Each measured propagation time is recorded in association with each position P _{i, j} . Further, the equal propagation time plane data unit 17 is a storage device, and stores data of the equal propagation time plane obtained in advance, for example, by ultrasonic propagation analysis. As shown in FIG. 2, the uniform propagation time plane is a plane formed by connecting the points obtained by aperture synthesis so that the round trip propagation times to the minute defect at that point are equal. Since this equal propagation time surface changes depending on the depth of the defect with respect to the focal point of the array-type ultrasonic probe 10, data of a plurality of equal propagation time surfaces for each defect depth is prepared. The output waveform data unit 15, the defect image composition processing unit 16, and the equal propagation time plane data unit 17 constitute a defect image reconstruction signal processing unit 20.

In the first embodiment, an equal propagation time plane is created by ultrasonic propagation analysis prior to the defect image synthesis process. Note that the present invention is not limited to this, and the creation of the equal propagation time plane may be performed during defect image synthesis.
The creation of the equal propagation time plane as shown in FIG. 2 can be performed by calculating the propagation time W by ultrasonic propagation analysis. This will be described based on the flowcharts of FIGS. 3, 4, and 5 and the explanatory diagram of FIG.

  FIG. 3 is a flowchart of the entire method for obtaining the ultrasound propagation time by the ultrasound propagation analysis, and FIG. 4 is a flowchart showing details of the processing S3 (acquisition of ultrasound waveform at the defect position) in FIG. FIG. 5 is a flowchart showing details of the processing S4 (acquisition of ultrasonic waveform received by the array probe and subjected to aperture synthesis processing) in FIG. 3, and FIG. 6 is an explanatory diagram showing the procedure of the method for obtaining the propagation time. It is. Here, FIG. 6 shows a two-dimensional analysis in the linear array probe. However, the present invention is not limited to this, and the shape of the array probe may not be linear, and the analysis may be performed in three dimensions.

(S1) An ultrasonic waveform transmitted from the transducer is set.
(S2) A path from each transducer of the ultrasonic probe to a preset minute defect (corresponding to the set internal defect of the present invention) is obtained. The upper part of FIG. 6 shows the paths of two vibrators.

(S3) An ultrasonic waveform at the defect position is acquired.
As detailed processing of (S3), the following processing is performed as shown in the flowchart of FIG.
(S3-1) Initialization of output ultrasonic waveform data.
(S3-2) Determine the vibrator 12 to be calculated.
(S3-3) The ultrasonic waveform at the position of the minute defect by the vibrator being calculated is calculated. At this time, if the transmission timing is different depending on the vibrator, the transmission is set at a time corresponding to the vibrator as shown in FIG. Also consider the propagation time and attenuation when propagating on the path. (See Figure 6)
(S3-4) The obtained ultrasonic waveform is added to the output ultrasonic waveform data.
(S3-5) Steps (S3-2) to (S3-4) are repeated until calculation is performed for all transducers used for transmission.
(S3-6) Output ultrasonic waveform data as an ultrasonic waveform at the defect position.
After such processing in FIG. 4, the processing shifts to processing (S4) in FIG.

(S4) An output waveform received by the array probe and subjected to aperture synthesis processing is acquired.
As the details of (S4), the following processing is performed as shown in the flowchart of FIG.
(S4-1) The ultrasonic waveform at the defect position is emitted from the minute defect position.
(S4-2) Initialize received waveform data of all transducers used for reception.
(S4-3) Determine the vibrator to be calculated.
(S4-4) The ultrasonic waveform received by the transducer being calculated is calculated (see FIG. 6).
(S4-5) Steps (S4-3) to (S4-4) are repeated until calculation is performed for all transducers used for reception.
(S4-6) The output waveform data after the focused beam processing is initialized.
(S4-7) Delay processing corresponding to actual focused beam processing is performed on the received waveform data of all the transducers (see FIG. 6).
(S4-8) The received waveform data of all the transducers subjected to the delay process are added to the output waveform data, respectively (see FIG. 6).
After such processing in FIG. 5, the processing shifts to processing (S5) in FIG.

(S5) The arrival time is read from the output waveform obtained in (S4) above. At this time, the method of reading the time includes setting a threshold value to acquire the rising time, setting the threshold value to acquire the falling time, and acquiring the time when the waveform reaches the peak value. Use the appropriate method.
(S6) The propagation time is obtained from the difference between the emission time from the probe and the arrival time. At this time, the method of reading the time includes acquiring a rise time by setting a threshold value, acquiring a fall time by acquiring the threshold value in the same manner, and acquiring a time at which the waveform has a peak value. Choose the appropriate method.

Next, a method for preparing data of the equal propagation time plane using the above method will be described.
FIG. 7 is a flowchart showing the method. This procedure is shown below.
(S21) The water distance (see the upper part of FIG. 6) is set.
(S22) A subject distance (see the upper part of FIG. 6) is set.
(S23) The aperture synthetic focus depth (for example, the depth position in the subject, see the upper part of FIG. 6) is set.
(S24) A deviation (in a plane perpendicular to the depth direction) between the subject and the aperture synthetic focus is set.
(S25) The propagation time is calculated from the waveform subjected to aperture synthesis processing (see the flowcharts of FIGS. 3, 4 and 5).
(S26) The above processing is performed until sufficient data is obtained to change the in-plane deviation perpendicular to the depth direction from the aperture synthetic focus within a range in which a defect signal can be received, and to create an equal propagation time plane. (S24) The operation of (S25) is repeated.
(S27) From the relationship of the amount of change in the propagation time with respect to the deviation in the plane orthogonal to the depth direction between the subject and the aperture synthetic focus obtained in the above processing (S24) (S25) (S26), the ultrasonic wave Using the propagation speed, the positions where the propagation times are equal are obtained, and the positions are connected to create the data of the equal propagation time plane. As shown in FIG. 8, the data on the equal propagation time plane is obtained by adjusting the depth of the minute defect so as to cancel the increase / decrease in the propagation time as a result. At this time, in the first embodiment, the propagation time and the equal propagation time plane are obtained as a difference from the value when the deviation from the aperture synthetic focal axis is zero.
(S28) From the above (S21) to (S27) until the equal propagation time planes corresponding to all the water distances, the object distances, and the aperture synthetic focal depths that can be necessary (for example, can be assumed in the measurement target) are obtained. Repeat the operation.

By the above method, an equal propagation time plane can be prepared for all water distances, object distances, and aperture synthetic focus depths that may be required. However, the creation method of the equal propagation time plane in the present invention is not limited to the above method, and data based on actual measurement or ultrasonic propagation simulation may be used. Further, the calculation method of the propagation time is not limited to the method shown in FIG. 3, FIG. 4, FIG. 5, and FIG.
If the area of each transducer is sufficiently large for the subject, the transducer can be further divided into a plurality of microregions, and processing can be performed by adding the signals of each microregion in units of each transducer. It ’s fine.
In addition, even when the area is large in the direction orthogonal to the array column direction (the depth direction in FIG. 7), the area may be divided into small regions in the orthogonal direction. (For example, a probe as shown in FIG. 24 is divided into a plurality of parts in the Y direction.)
Further, although the example in which the transducers are arranged only in the one-dimensional direction has been described, an array type probe arranged in two dimensions can be applied if processing is performed in two dimensions.

  FIG. 9 is an example of the data of the equal propagation time plane obtained as described above. This is stored in the uniform propagation time plane data unit 17 of FIG. 1 and the defect image synthesis processing unit 16 synthesizes the defect image. Used when

Next, the operation of the ultrasonic imaging apparatus in FIG. 1 will be described.
FIG. 10 is a flowchart showing processing when a defect image is synthesized in the ultrasonic imaging apparatus of FIG.
(S31) The array-type ultrasonic probe 10, the drive element selection circuit, and the array signal processing circuit are operated to scan the focal point formed by aperture synthesis, and the output waveform data unit 15 includes the drive element selection circuit 12, Based on the outputs of the receiving circuit 13, the array signal processing circuit 14, the x-direction position detection means 21 and the y-direction position detection means 22, output waveform data corresponding to each position P _{i, j} is detected.
(S32) As shown in FIG. 11, the array signal processing circuit 14 or the defect image composition processing unit 16 calculates the water propagation time and the reflection waveform at P _{i, j} having the largest defect echo in the output waveform data. The object propagation time is detected, and the water distance and the object distance are acquired from the propagation time.
(S33) The defect image synthesis processing unit 16 stores the water distance / subject distance and the aperture synthesis focus in the data of the equal propagation time plane stored in the equal propagation time plane data unit 17 (see FIG. 9). A depth setting value close to the water distance / subject distance and aperture synthetic focus depth obtained in (S32) above is selected. In the first embodiment, as shown in FIG. 12, the subsequent processing is performed using only one uniform propagation time plane shape selected here. FIG. 12 shows a method of drawing an equal propagation time plane at different propagation times using one equal propagation time plane. The propagation time is equal to the equal propagation time plane of the propagation time T2. Even when they are different (T1, T3), an equal propagation time plane having the same shape as the equal propagation time plane of the propagation time T2 can be used (in this case, data of one equal propagation time plane is stored). If it is enough).

(S34) The defect image composition processing unit 16 performs an imaging process using the data on the equal propagation time plane selected in (S33) above. FIG. 13 shows an imaging processing method according to the first embodiment. Here, in FIG. 13, the description is made in two dimensions for simplicity, but in the first embodiment, the processing is performed in three dimensions. However, the present invention is not limited to this, and the processing may be performed in two dimensions. The procedure of the imaging processing method in the first embodiment is shown below.
(A) each focal position P _i, the focus position P _i which defect echo is detectable among _j, for _j, to detect the propagation time as in FIG. 11. The detection of the propagation time may be performed by the array signal processing circuit 14 in FIG. 1 or the defect image composition processing unit 16, and is performed by the array signal processing circuit 14 in this embodiment.
(B) A region where a defect may exist in the subject 1 is divided into minute volume elements, and each of the minute volume elements has a three-dimensional address Pf _{k, l, m} (k: position in the x direction, l: in the y direction) Position, m: position in the Z direction).
(C) From the propagation time at each position P _{i, j} , the defect position when the defect is assumed to be on the probe center axis is calculated, and Pf _{k, l, m} corresponding to the defect position is calculated as shown in FIG. Thus, it is set as the center of the equal propagation time plane.
(D) Each small region Pf _k in which an equal propagation time plane (see FIG. 12) is formed from the center of the equal propagation time plane set in (c) above and a part of the equal propagation time plane exists. _{, l, m} , count 1 is added to the counter C _{k, l, m} provided at Pf _{k, l, m} .
(E) The above operations (c) and (d) are performed for all positions P _{i, j at} which defect echoes can be detected.

(S35) The data obtained in (S34) is visualized. The imaging method in the first embodiment is as follows.
(A) For all (k, l) _, the maximum value Cmax (k, l) of C _{k, l, m} when (k, l) is fixed is obtained.
(B) For each (k, l) where Cmax (k, l) is greater than or equal to the threshold value, a different threshold value is determined and the counter C _{k, l, m} is checked from the smaller m side. Let m (k, l) be m above the threshold.
(C) Using m (k, l) obtained in (b) above, connecting adjacent centers of each minute region corresponding to each (k, l, m (k, l)) with a line Constructs a polygon.
(D) The polygon obtained in the above (c) is three-dimensionally displayed.
The imaging method is not limited to the three-dimensional polygon display method as described above, and may be another three-dimensional display method or a two-dimensional display method.

  Here, an ultrasonic beam focusing array probe having a frequency of 50 MHz, an array pitch of 100 μm, 32 channels used for aperture synthesis, and an underwater focal length of 15 mm of a line focusing beam (a transducer in a direction orthogonal to the array arrangement direction as shown in FIG. 17). The surface has a curvature and converges in that direction.), An artificial hole with a diameter of 300 μm is made in the steel slab sample, the hole is flawed as shown in FIG. An example is shown in FIG. Note that FIG. 14B uses an equal propagation time plane that is created by further dividing each vibrator into minute regions. FIG. 14C is a diagram in which the imaging process is performed by the method described in Patent Document 3 and three-dimensionally displayed by the defect image synthesis method (S35). In FIG. 14C, the image of the artificial hole is flat in the z direction, whereas in FIG. 14B, the curved surface of the artificial hole is reproduced, and the shape resolution is improved. Recognize.

Embodiment 2. FIG.
The second embodiment is an example in which the defect image composition processing unit 16 in FIG. 1 performs processing different from the above arithmetic processing. The defect image composition processing unit 16 according to the second embodiment uses delay time data instead of the above equal propagation time plane data. Therefore, a storage device (not shown) for storing delay time data is provided in place of the equal propagation time plane data unit 17. This delay time data (delay time group) is obtained from propagation time change amount data (data before the conversion in FIG. 8), and as shown in the conceptual diagram of FIG. 15, the propagation time change amount. The longer the delay time, the smaller the delay time, and the shorter the change amount, the larger the delay time. Similarly to the equal propagation time plane data, it is obtained corresponding to each value of water distance, subject distance, and aperture synthetic focal depth, and stored in the storage device.

In the flowchart shown in FIG. 10, the defect image composition processing unit 16 differs in the specific contents of the equal propagation time plane selection process (S33) and the data visualization process (S34), but the other processes are the same. is there.
The equal propagation time plane selection process (S33) is a delay time data selection process. Specifically, processing for selecting delay time data (delay time group) corresponding to the water distance and defect depth of the received waveform measured by the array type ultrasonic probe is performed.
In the data visualization process (S34), the waveform resynthesis process is performed as shown in FIG. 15 using the delay time data selected in the delay time data selection process.

  Specifically, a predetermined number of adjacent focal positions (10 points in the example of FIG. 15) are selected from a number of focally scanned points, and the selected delay time data with respect to the reflected waveform data measured at those 10 points. Corresponding to (delay time group), the waveform is delayed at each probe position. As shown in FIG. 15, the delay time is reduced for the signal of the outer focus, and the delay time is increased for the inner focus. As a result, if there is a defect above and below the focal point located at the center of the predetermined number of focal positions, the defect signal is emphasized and the presence of the defect can be detected by aligning the defect waveforms. On the other hand, if there is no defect above and below the focal point located at the center, for example, if there is a defect directly above or below the outer focal point, the signal of the defect received at each focal point is not aligned even if delayed. The defect signal cannot be detected without being offset and emphasized. That is, there is no defect immediately above or below the focal point located at the center.

  An aperture synthesis waveform is obtained by selecting and repeating a predetermined number of data in order while moving the selection range with respect to data obtained by measuring such a process at a number of points. Then, when selecting the delay time data (delay time group), the delay time data (delay time group) corresponding to a plurality of depths is selected, and the above arithmetic processing is repeated. Then, the obtained waveform is displayed by an appropriate method (A scope, B scope, C scope, three-dimensional display).

Embodiment 3. FIG.
The third embodiment is an example in which the ultrasonic propagation analysis portion is different from the first embodiment.
The ultrasonic wave propagation analysis in the third embodiment is as follows.
FIG. 16 is a flowchart illustrating a propagation analysis method according to the third embodiment.
(S′1) For example, as shown in FIG. 17, a beam is virtually emitted from a preset minute defect in a plurality of directions, and the intersection with the array probe transmission / reception surface ahead of the extended beam is obtained. The intersection point is a point set on the array probe transmission / reception surface (hereinafter referred to as probe set point). When the virtual beam is extended, ultrasonic waves are refracted at the boundary between the media having different acoustic impedances (such as the boundary between the subject and water), and the virtual beam is also refracted accordingly. Although only two points, point 1 and point 2, are shown in FIG. 17, the probe set points are densely obtained in order to actually divide the array probe transmission / reception surface into a small area. Preferably, the density is set such that at least two probe set points can be set for one transducer of the array probe. At this time, the path between the probe set point and the micro defect is equal to the path of the virtual beam that has been traced.

(S′2) For example, as shown in FIG. 18, a minute area is set using a midpoint between adjacent probe set points.
(S′3) A process similar to the process of (S1) in the first embodiment is performed.
(S′4) For example, as shown in FIG. 19, the ultrasonic waveforms emitted from all the minute areas on all the transducers used for transmission are calculated and added. As the route at this time, the route obtained in the process (S′1) is used. Here, the details of the processing of (S′4) shown in FIG. 19 are as follows.

(S4′-1) Initialization of output ultrasonic waveform data.
(S4′-2) Determination of a small area to be calculated (on the vibrator used for transmission).
(S4′-3) Calculate an ultrasonic waveform at a minute defect position based on the calculated minute area.
(S4′-4) The obtained ultrasonic waveform is added to the output ultrasonic waveform data.
(S4′-5) The above processes (S′4-2) to (S′4-4) are repeated until calculation is performed on a small area on all the transducers used for transmission.
(S4'-6) Output ultrasonic waveform data is output as an ultrasonic waveform at the defect position.
As described above, the process of (S′4) is completed, and the process proceeds to (S′5) of FIG.

(S′5) For example, as shown in FIG. 20, for the ultrasonic waves emitted from the minute defects and directed to the array probe, first, the ultrasonic waveforms received by all the minute areas on all the transducers used for reception are received. get. Next, the ultrasonic waveforms are added for each transducer. Finally, after delay processing corresponding to the focused beam processing is performed on each transducer, the ultrasonic waveforms of all the transducers are added to obtain a final output waveform. Here, the details of the processing of (S′5) shown in FIG. 20 are as follows.

(S5′-1) The ultrasonic waveform at the defect position is emitted from the minute defect position.
(S5′-2) Initialization of received waveform data of all the transducers used for reception.
(S5′-3) Determine the vibrator to be calculated.
(S5′-4) Calculate an ultrasonic waveform received at one minute area in one transducer being calculated.
(S5′-5) The obtained ultrasonic waveform is added to the received waveform data of the transducer being calculated.
(S5′-6) The processes of (S5′-4) and (S5′-5) are repeated for all the small areas on one vibrator being calculated.
(S5′-7) The above processes (S5′-4) to (S5′-6) are repeated for all transducers used for reception.
(S′5-8) The output waveform data after the focused beam processing is initialized.
(S′5-9) Delay processing corresponding to the actual focused beam processing is performed on the received waveform data of all the transducers.
(S′5-10) The received waveform data of all the transducers subjected to the delay process are added to the output waveform data.
As described above, the process of (S′5) is completed, and the process proceeds to (S′6) of FIG.

(S′6) The same process as the process of (S5) in the first embodiment is performed.
(S′7) The same process as the process of (S6) in the first embodiment is performed.

  As described above, the feature of the third embodiment is that the path (path) obtained by the method shown in FIG. 17 as the path between the micro defect and the micro area on the probe used in (S′4) and (S′5). The method of determining the starting point of the route and the direction of travel first and finding the end point of the route later is used. That is, in the third embodiment, when dividing a plurality of regions of each transducer, an ultrasonic propagation path from the set internal defect in a plurality of directions is calculated, and an intersection of the path and the ultrasonic probe is calculated. Then, using the obtained intersection, the ultrasonic probe surface is divided into a plurality of areas with the obtained intersection as a representative point, and the inside of the setting corresponding to each area of the divided ultrasonic probe and each divided area The propagation of the ultrasonic wave between the defect and the defect is calculated as propagating through the propagation path traced when calculating the intersection of the ultrasonic wave propagation path and the ultrasonic probe. For this reason, in the third embodiment, more efficient calculation is possible as compared with a method in which the starting point and the ending point of a route are determined first and an intermediate route is obtained later as in the conventional example shown in FIG.

Embodiment 4 FIG.
The fourth embodiment is an example in which the ultrasonic propagation analysis portion is different from the first and third embodiments.
The ultrasonic wave propagation analysis in the fourth embodiment is as follows.
FIG. 21 is a flowchart illustrating a propagation analysis method according to the fourth embodiment.
The difference between the processing of FIG. 21 and FIG. 16 is that in (S′2), the probe probe is used to divide the array probe into a small area, but in (S ″ 2), the probe probe is not used. The point is to cut into a small area by a method such as cutting on a mesh.

(S ″ 1) The same as (S′1) in the third embodiment.
(S ″ 2) As described above, for example, a small area is cut by a method such as cutting on an equally divided mesh.
(S ″ 3) It is the same as the processing of (S′3) in the third embodiment.
(S ″ 4) and (S ″ 5) are calculated according to FIG. 19 and FIG. 20 in the same manner as (S′4) and (S′5) of Embodiment 3, respectively. The method of calculating the ultrasonic propagation, i.e. propagation time and / or attenuation, from the defect and the microdefect to the array probe is different.

FIG. 22 is an explanatory diagram of a calculation method of propagation time and attenuation in the fourth embodiment.
In FIG.

Since it is the probe set point obtained in (S ″ 1) and the path between this point and the micro defect is known, the propagation time and / or attenuation can also be calculated. From the propagation time and / or attenuation of these points, the propagation time and / or attenuation at a representative point on a small area is obtained by interpolation or extrapolation, for example, by the method shown in FIG.
In the case of the example of FIG. 22, since the propagation time and / or attenuation is approximated by a linear expression of coordinates, the probe set point to be used is preferably close to the representative point on the minute area.
Except for calculating the ultrasonic wave propagation from the minute area on the array probe to the minute probe and from the minute defect to the array probe using the propagation time and / or attenuation obtained as described above, it is the same as in the third embodiment. .

(S ″ 6) and (S ″ 7) are the same as (S′6) and (S′7) of Embodiment 3, respectively.
About the part which is not described above, it carries out by the method similar to said Embodiment 1. FIG.

  As described above, in the fourth embodiment, in (S ″ 4) and (S ″ 5), first, ultrasonic propagation is calculated using the path between the set point on the probe and the minute defect, and the minute area and minute amount are calculated. Ultrasonic propagation between defects is obtained by interpolation or extrapolation. That is, in the fourth embodiment, when obtaining the waveform of the reflected wave from the set internal defect received by each divided region of each transducer, the propagation path of the ultrasonic wave from the set internal defect in a plurality of directions is calculated. Then, the intersection of the path and the ultrasonic probe is calculated, and the propagation of the ultrasonic wave between the obtained intersection and the set internal defect corresponding to each divided area is calculated as the ultrasonic propagation path and the ultrasonic probe. The propagation waveform of the ultrasonic wave between each divided area of each transducer and the set internal defect is calculated as the propagation path traced when calculating the intersection with Since the calculation is performed by interpolation or extrapolation from the propagation waveform of the ultrasonic wave propagating between the defects, efficient calculation is possible as in the third embodiment.

  DESCRIPTION OF SYMBOLS 10 Array type ultrasonic probe, 11 Transmitter circuit, 12 Drive element selection circuit, 13 Receiver circuit, 14 Array signal processing circuit, 15 Output waveform data part, 16 Defect image composition processing part, 17 Equal propagation time plane data part, 20 Defect Image reconstruction signal processing unit, 21 x-direction position detection means, 22 y-direction position detection means.

Claims (5)

The focus formed by interposing water between the array-type ultrasonic probe and the subject and subjecting the reception signal of the array-type ultrasonic probe to aperture synthesis is scanned relative to the subject. While transmitting and receiving an ultrasonic wave toward the subject and receiving a reflected wave from an internal defect of the subject;
A signal processing step of performing aperture synthesis processing on the signal received by each transducer of the array-type ultrasonic probe;
A signal generation step of generating a signal by adding the resultant aperture synthesized waveform after being delayed by a set delay time; and
An ultrasonic imaging method of an internal defect comprising a display step of displaying the generated signal,
The delay time is
By calculating the propagation time based on the aperture synthesis waveform, the amount of change in the propagation time with respect to the relative position between the focus of the aperture synthesis processing performed on the received signal of each transducer of the array-type ultrasonic probe and the set internal defect is obtained. An ultrasonic imaging method of an internal defect, which is set from the amount of change in the propagation time.   The amount of change in the propagation time is determined by dividing each transducer into a plurality of regions, obtaining a waveform of a reflected wave from a set internal defect received by each divided region, and synthesizing the waveform for each transducer. The ultrasonic imaging method for internal defects according to claim 1, wherein the calculation is performed by using the signal of each transducer. When dividing the plurality of regions of each vibrator,
Calculate the propagation path of ultrasonic waves in multiple directions from the set internal defect,
Calculate the intersection of the path and the ultrasound probe,
Using the obtained intersection point, the ultrasonic probe surface is divided into a plurality of areas with the obtained intersection point as a representative point, and each divided ultrasonic probe area and the set internal defect corresponding to each divided area, The ultrasonic wave propagation between the ultrasonic wave and the ultrasonic probe is calculated on the assumption that the ultrasonic wave propagates through the propagation path traced when calculating the intersection of the ultrasonic wave propagation path and the ultrasonic probe. Sonic imaging method. When obtaining the waveform of the reflected wave from the set internal defect received by each divided region of each vibrator,
Calculate the propagation path of ultrasonic waves in multiple directions from the set internal defect,
Calculate the intersection of the path and the ultrasound probe,
It is assumed that the propagation of ultrasonic waves between the obtained intersection and the set internal defect corresponding to each divided area propagates through the propagation path traced when calculating the intersection of the ultrasonic propagation path and the ultrasonic probe. Calculate
The ultrasonic wave propagation waveform between each divided area of each transducer and the set internal defect is interpolated or extrapolated from the wave propagation waveform between the intersection near each area and the set internal defect. The ultrasonic imaging method of internal defects according to claim 2, wherein The focus formed by interposing water between the array-type ultrasonic probe and the subject and subjecting the reception signal of the array-type ultrasonic probe to aperture synthesis is scanned relative to the subject. While transmitting and receiving ultrasonic waves toward the subject, and receiving reflected waves from internal defects of the subject;
Signal processing means for performing aperture synthesis processing on a signal received by each transducer of the array-type ultrasonic probe;
A signal generating means for generating a signal by delaying the obtained aperture synthetic waveform by the set delay time data and adding the signal;
An ultrasonic imaging method of an internal defect comprising display means for outputting and displaying the generated signal data in an image memory,
The delay time data is
The propagation time is calculated based on the synthetic aperture waveform, and is calculated from the amount of change in the propagation time with respect to the relative position between the focal point of the synthetic aperture processing performed on each transducer signal of the array-type ultrasonic probe and the set internal defect. An ultrasonic imaging apparatus for internal defects, which is set from the amount of change in the propagation time.

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