JP2008309697A - Ultrasonic section inspection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of a tooth omission during inspection in application of ultrasonic flaw detection using an oscillator array to a subject transferred at high speed. <P>SOLUTION: When a section of the subject is inspected using the oscillator array including a large number of unidimensionally arranged ultrasonic oscillators, ultrasonic waves are transmitted from a part of or all of ultrasonic oscillators of the oscillator array, reflected waves generated by the transmitted ultrasonic waves are received using a part or all of the ultrasonic oscillators of the oscillator array, and the received signals are converted to digital waveform signals. Based on a distance between each oscillator of an ultrasonic oscillator group composed of a plurality of ultrasonic oscillators selected from the oscillator array and a continuous receiving focal position formed in the subject, the time axis of the digitized received signal of each oscillator is converted, and a curtain of received needle beams is formed under the oscillator array by adding and composing the received signal with converted time axis of each oscillator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic cross-sectional inspection method and apparatus, and in particular, by scanning an ultrasonic inspection apparatus or ultrasonic transducer that performs ultrasonic inspection on an object that is continuously conveyed. The present invention relates to an ultrasonic cross-sectional inspection method and apparatus suitable for use in an ultrasonic inspection apparatus for inspecting a subject.

  Industrial products such as metal materials are often inspected using ultrasonic waves in order to confirm that there are no harmful defects inside. In recent years, ultra-fine internal defects of about φ20μm have been made into metal to reduce the thickness of metal materials for weight reduction, change the manufacturing process for environmental measures, and improve internal quality for longer life. It has become necessary to detect the entire length and cross section of the material. In order to inspect the full length and the entire cross section of the total number of manufactured metal material products, it is necessary to inspect the products conveyed in the production line. The conveyance speed of the product that needs to detect the ultra-fine defect is about 1000 mm / s at the maximum. Accordingly, it is necessary to detect an ultra-fine defect having a size of about φ20 μm over the entire length and the entire cross section of a product conveyed at a high speed of 1000 mm / s.

  The inspection apparatus using the ultrasonic waves is called an ultrasonic flaw detector. In these apparatuses, a technique of electronically scanning an ultrasonic beam for the purpose of high-speed inspection is used to detect the internal defect. Among these, a scanning method called linear electronic scanning which has been conventionally used will be described with reference to FIG.

FIG. 6 is a block diagram showing a configuration of a conventional ultrasonic inspection apparatus. In FIG. 6, 101 indicates a transducer array. The transducer array 101 has a number of ultrasonic transducers (hereinafter simply referred to as “elements”) arranged in an array at equal intervals at the tip, and a plurality of elements are driven and determined as a set. Focus the ultrasonic beam into position. In the illustrated example, the total number of elements is 64 (101 _{1 to} 101 ₆₄ ), and the number of elements used in one set is eight. Element numbers 1 to 64 are assigned to the respective elements. B _{1 to} B ₅₇ denote ultrasonic beams formed by the elements 101 _{1 to} 101 ₆₄ . A control circuit 102 controls transmission / reception of the ultrasonic beams B _{1 to} B ₅₇ .

Here, an outline of the transmission / reception operation of the ultrasonic beams B _{1 to} B ₅₇ will be described. First, by driving _eight elements 101 _{1 to} 101 ₈ as a set, an ultrasonic beam B ₁ having a focusing point on the center line of the elements 101 _{1 to} 101 ₈ is transmitted and received. By then driving the element 101 _{2-101 9} as one set, the ultrasonic beams B ₂ having a focal point on the element 101 _{2-101 9} centerline transmitting and receiving waves. Similarly, the drive element group is shifted one by one, and finally the ultrasonic beam B ₅₇ is transmitted and received by driving the elements 101 _{57 to} 101 ₆₄ . By such an operation, an ultrasonic beam is electronically scanned on the subject at a pitch equal to the element arrangement pitch. Control necessary for the transmission / reception of the focused ultrasonic beam and the electronic scanning described above is performed by the control circuit 102 connected to the transducer array 101.

  Note that the transmission beam can be focused by changing the application timing of the electric pulse applied to each element in order to transmit the ultrasonic wave in the one set of elements. The focusing of the received beam can be achieved by adding the signals received by the one set of elements while delaying each element for an individual time.

  The linear electronic scanning described above is said to be capable of high-speed inspection about 20 times as compared with a method of performing mechanical scanning of an ultrasonic probe. However, when a subject transported at a high speed of about 1 m / second in a transport line of metal material or the like is to be inspected using the linear electronic scanning, a considerable amount of the subject must be observed before one electronic scanning is completed. Since the length of the portion passes, there is a problem that missing teeth occur in the inspection.

  As a prior art for speeding up the inspection by linear electronic scanning, Patent Document 1 is cited. This patent document 1 describes, “In an ultrasonic inspection apparatus that scans an ultrasonic beam along an array of a large number of ultrasonic vibration elements, a beam area section that divides all of the ultrasonic beams into a plurality of continuous beam areas. Means, a beam area selection means for selecting each of the beam areas in a predetermined order, and a shift means for sequentially shifting one ultrasonic beam in the selected beam area each time the beam area is selected. It has been proposed to increase the speed of linear electronic scanning.

  Patent Document 2 is cited as a prior art for speeding up the cross-sectional inspection of a subject. This Patent Document 2 states that “an ultrasonic transducer array having a plurality of transducers that can be arranged along the surface of a test material, an excitation unit that excites each transducer of the ultrasonic transducer array with a spike pulse, Waveform memory that stores ultrasonic reception echoes received by transducers as waveform data for each transducer, and phase synthesis that reads out the contents of the waveform memory that stores the waveform data for each transducer and performs phase synthesis using an adder And a focus means for giving the address of each waveform memory as an address corresponding to the beam path distance of the dynamic focus with respect to an arbitrary position within the electronic scanning range in reading out the waveform memory. It has been proposed to speed up the cross-sectional inspection of the subject by using the “apparatus”.

Japanese Patent Laid-Open No. 3-248058 JP 2003-28846 A

  However, in Patent Document 1, the scanning of the ultrasonic beam is performed by electronic switching, and the situation is far from solving the problem of missing teeth in the inspection described above.

  In Patent Document 2, it is necessary to sequentially change the depth position of the focal point when forming the focal point of the received wave from all the received signal data of the transducer array stored in the waveform memory. There was a problem that took time. [0042] of Patent Document 2 shows an example in which one cross-sectional inspection is completed in 1 ms. For example, when the speed of the test material is 1000 mm / s (60 mpm), the cross-sectional inspection is only performed every 1 mm. The test material cannot be inspected. In this case, for example, even if a specimen has a circular plane defect of about φ100 μm, the probability that an ultrasonic beam hits the defect perpendicularly is smaller than 1/10.

  In Patent Document 2, the focus of a received beam is formed at a specific position by phase-combining all n received signals received by n elements. 200 is illustrated as n. Since the diameter of the received beam at the focal position is inversely proportional to the size of the aperture, it is likely that n is large from the viewpoint of defect detection capability and resolution improvement. However, since the individual ultrasonic transducers (also referred to as elements) that constitute the transducer array have a certain width in the arrangement direction, the receiving directivity of the individual ultrasonic transducers has a certain narrow angle range. Limited to. For example, assuming that the nominal frequency of the transducer array is 5 MHz and the element width in the arrangement direction is 0.8 mm (the element width of a general 5 MHz transducer array is about this), reception at the center axis of the received beam The angle at which the receiving efficiency is within −6 dB with respect to the efficiency (referred to as receiving directivity) is about 12 ° (with respect to the beam center axis).

  Consider using this transducer array to form a focal point at a distance of 50 mm from the transducer array using only elements with a receiving directivity with respect to the focal point of -6 dB or less. Assuming that the element located immediately above the focal point is the element i, the element j having a wave receiving directivity with respect to the focal point within −6 dB is located about 11 mm from the element i. Since the element width is 0.8 mm, the element j is the thirteenth to fourteenth elements from the element i. Therefore, in the above case, the number of elements mainly contributing to the focus of the received beam is less than 30 in total.

  As described above, even when the technique disclosed in Patent Document 2 is applied to the above general case, there is a problem that the phase synthesis processing of 80% or more elements is wasted. Furthermore, when the apparatus shown in Patent Document 2 is applied to on-line flaw detection at a manufacturing site, periodic noise peculiar to the site included in a signal received by 80% or more of elements that hardly contribute to focus formation is added. Therefore, there is a problem that a noise signal having a large amplitude is likely to be generated. A noise signal having a large amplitude is a problem that is most disliked in online flaw detection because it causes false detection.

  The present invention has been made to solve the above-described conventional problems, and in applying ultrasonic flaw detection using a transducer array to an inspection of an object to be transported at high speed, no tooth loss occurs in the inspection. The challenge is to do so. Furthermore, an object of the present invention is to provide a flaw detection method and apparatus in which noise having a large amplitude does not occur.

  When inspecting a cross section of a subject using a transducer array composed of a large number of ultrasonic transducers arranged one-dimensionally, the present invention can apply ultrasonic waves from a part or all of the ultrasonic transducers. And the reflected wave generated by the transmitted ultrasonic wave is received using a part or all of the ultrasonic transducers of the transducer array, and the received signal is digitally transmitted. Each of the transducers of the first ultrasound transducer group that is converted into a waveform signal and is composed of a plurality of ultrasound transducers selected from the transducer array, and the continuous reception formed inside the subject. A cross-sectional inspection method using ultrasonic waves, which converts a time axis of a digitized received signal of each transducer based on a distance from a wave focus and simultaneously adds and synthesizes the converted received signals of each transducer. The transducer array is composed of a plurality of ultrasonic transducers. Grouped into a group of ultrasonic transducers different from the first ultrasonic transducer group, and in each group, a plurality of signals received by a plurality of ultrasonic transducers in the group have different delays. In addition, the above-described problems are solved by adding the plurality of delayed signals into one signal.

  Here, a plurality of first ultrasonic transducer groups including a plurality of ultrasonic transducers can be provided, and addition and synthesis can be simultaneously performed in the plurality of ultrasonic transducer groups.

  The present invention is also an apparatus for inspecting a cross section of a subject using a transducer array composed of a large number of ultrasonic transducers arranged one-dimensionally, and a part or all of the ultrasonic transducers of the transducer array. Means for transmitting an ultrasonic wave from the apparatus, means for receiving a reflected wave generated by the transmitted ultrasonic wave using a part or all of the ultrasonic transducers of the transducer array, and the receiving unit. Means for converting a wave signal into a digital waveform signal; each transducer of a first ultrasonic transducer group composed of a plurality of ultrasonic transducers selected from the transducer array; The means for converting the time axis of the digitized received signal of each transducer based on the distance from the continuous received focus position formed inside the specimen, and the converted received signal of each transducer simultaneously An ultrasonic cross-sectional inspection device equipped with a means for addition synthesis The transducer array is divided into groups of ultrasonic transducers that are different from the first ultrasonic transducer group, and each group includes a plurality of ultrasonic transducers. A delay unit that adds different delays to the plurality of signals received by the ultrasonic transducer; and an addition unit that adds the plurality of delayed signals into a single signal.

  Here, the means for adding and synthesizing can simultaneously add and synthesize the plurality of first ultrasonic transducer groups.

  In the present invention, ultrasonic waves are transmitted from a part or all of the ultrasonic transducers of the transducer array, and the reflected waves generated by the transmitted ultrasonic waves are transmitted to a part or all of the transducer arrays. An ultrasonic wave received by an ultrasonic transducer, converted from the received signal into a digital waveform signal, and composed of a plurality of ultrasonic transducers selected from the transducer array Based on the distance between each transducer of the transducer group and the continuous receiving focus position formed inside the subject, the time axis of the digitized received signal of each transducer is converted, and each oscillation Since the converted reception signals of the child are added and synthesized at the same time, a curtain of the reception needle beam can be formed under the transducer array. Therefore, in the inspection of an object moving at high speed, there is no occurrence of inspection missing due to linear electronic scanning, and in particular, there is an unprecedented advantage that the entire volume of an object moving at high speed can be inspected. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a simplified example of the embodiment, FIG. 2 is an explanatory diagram showing a point of interest in this embodiment, and FIG. 3 is a diagram showing the time of propagation of ultrasonic waves between the two specified elements and the focal point. FIG. 4 is a block diagram showing an overall image of the present embodiment.

  As an embodiment, a case will be described in which the total number of elements is 384, and the number of elements in one set used to form a received focused beam is 24. In the present embodiment, 24 thin elements are used to form one narrow receiving beam (hereinafter referred to as a needle beam) having a continuous focal point below the center of the arrangement direction, and a selection from all 384 elements is possible. An example of forming a receiving needle beam curtain in which receiving needle beams are arranged directly below the transducer array 1 by forming receiving needle beams simultaneously under an array of 24 element groups is shown. Yes. In the present embodiment, the focus of the received focused beam is made continuous with 24 elements.

As shown in FIG. 1 (simplified view) and FIG. 4 (overall view), in this embodiment, ultrasonic waves are transmitted from the transducer array 1 and the elements 1 ₁ to 1 _{384 of the} transducer array 1. , reception amplifier 3 ₁ to 3 ₃₈₄ to pulser 2 ₁ to 2 ₃₈₄ that apply electric pulses to elements ₁ 1 to 1 _384, each device ₁ 1 to 1 ₃₈₄ amplifies the ultrasonic signal received by, Delay elements 4 ₁ to 4 ₃₈₄ for delaying the amplified ultrasonic signals received in units of multiple elements (in the figure, 4 elements, hereinafter referred to as groups), and the delayed received ultrasonic signals to multiple elements ( Adder / synthesizers 5 _{1 to} 5 ₃₈₄ (four subscripts are shown in the figure) for adding and synthesizing as four elements in the figure, and A / D for converting the received ultrasonic signal after addition and synthesis into a digitized received signal Converters 6 _{1 to} 6 ₃₈₄ (in the figure, subscripts are every 4th), time of digitized received signal Time axis converters 11 _{1 to} 11 ₃₈₄ for converting axes (in the figure, subscripts are every fourth), waveform memories 12 _{1 to} 12 ₃₈₄ for storing signals whose time axes have been converted, and stored time axis conversion signals Is used to generate a reception signal equivalent to reception by a single needle beam with a continuous focal point formed immediately below between the transducers 1i and 1i + 1. Become.

That is, in this embodiment, for each element of the transducer arrays 1 ₁ to 1 ₃₈₄ , the pulsars 2 ₁ to 2 ₃₈₄ , the receiving amplifiers 3 _{1 to} 3 ₃₈₄ , the delay elements 4 ₁ to 4 ₃₈₄ , and the waveform memory 12 ₁ ~ 12 ₃₈₄ are provided. In addition, in the ratio of one for a plurality of elements (4 in the figure), the adder / synthesizers 5 _{1 to} 5 ₃₈₄ (in the figure, subscripts are every four), and the A / D converters 6 _{1 to} 6 ₃₈₄ (in the figure, the subscripts are 4), time axis converters 11 _{1 to} 11 ₃₈₄ (in the figure, subscripts are every 4th).

Here, the roles of the delay elements 4 ₁ to 4 ₃₈₄ and the adder / synthesizers 5 _{1 to} 5 ₃₈₄ (subscripts are every 4th in the figure) will be described in detail. The delay elements 4 ₁ to 4 ₃₈₄ are drawn with the same length every fourth interval in the figure. This means that the delay time of the signal by the element is the same. The delay elements 4 ₁ to 4 ₃₈₄ respectively delay the received ultrasonic signals from the receiving amplifiers 3 _{1 to} 3 ₃₈₄ input into the group by different times. The received ultrasonic signals delayed by different times by the delay elements 4 ₁ to 4 ₃₈₄ are added and synthesized by the adder / synthesizers 5 _{1 to} 5 _{384 and} combined into one signal.

The delay time in the group of delay elements is set so that a fixed time Δt is added to the increment of the subscript. As Δt, a sufficiently long time is selected so that echo signals from the same echo source received by adjacent elements do not cause interference in the addition synthesis in the addition synthesizer 5 _j-4 . With this configuration, the signals received by the transducer arrays 1 _j-4 to 1 _j-1 and amplified by the receiving amplifiers 3 _{j-4 to} 3 _j-1 are retained in the form of individual signals. Since the signals can be combined into one signal, the manufacturing cost can be greatly reduced by reducing the number of expensive A / D converters.

FIG. 2 shows the concept of receiving needle beam formation in this embodiment. Ultrasonic waves are transmitted from all the elements 1 ₁ to 1 _{384 of the} transducer array 1. In addition, an ultrasonic reflection signal (echo) from the subject is received using all the elements ₁₁ to ₃₈₄ of the transducer array 1. Signal by ultrasonic wave reception by the elements 1 ₁ to 1 ₃₈₄ are amplified by the reception amplifier 3 ₁ to 3 ₃₈₄ shown in FIG. 1, respectively, digital by the A / D converter 41 _{to 384} Converted to a signal. After performing phase matching of these digitized signals, addition and synthesis can be performed to form a received focused beam as shown in FIG.

In the present embodiment, as shown in FIG. 2, when a receiving beam focus is formed at a distance F _R from the transducer array 1 below the elements 1 _i-12 to 1 _{i + 11} , the element 1 _i− the distance between the ₁₂ to 1 i + ₁₁ and the focal point is focused to be expressed by a function which increases monotonically with increasing distance F _R. In the example shown in FIG. 2, since the set focus directly under the center of the 1 _i-1 and 1 _i, the closest element to the focus is 1 _i-1 and 1 _i. FIG. 3 shows a comparison between the time for which the ultrasonic wave propagates between the element and the focal point and the time for the ultrasonic wave to propagate between the element 1 _i-12 farthest from the focal point and the focal point. In this calculation, the ultrasound velocity in medium ultrasound propagates to 1500 m / s, the element pitch p and 0.2 mm, was changed F _R to 4Mm～25mm.

As shown in FIG. 3, the time required for the ultrasonic wave to propagate between the two elements and the focal point has a monotonously changing functional relationship (hereinafter referred to as a propagation time relative relationship). Here, the horizontal axis in FIG. 3 is obtained by converting the distance d _i-1 in FIG. 2 into the propagation time, and the vertical axis is obtained by converting the distance d _i-12 in FIG. 2 into the propagation time. Therefore, the time axis of the signal received by one element (the time of reception) is matched with the time axis of the signal received by the other element (the time of reception) using the relationship shown in FIG. if (hereinafter, referred to as time axis conversion), also vary the distance F _R between the focus and the transducer array 1, it is always possible to match the two phases.

The relationship between the time for the ultrasonic wave to propagate between the element 1 _i-1 and the focal point and the time for the ultrasonic wave to propagate between the element other than the element 1 _i-12 and the focal point are the same as in FIG. because there are, these relationships precomputed, by performing time-axis conversion of the signals received, regardless of the distance F _R between the focus and the transducer array 1, similarly, the element 1 _i-12 than the element And the phase of the element 1 _i-1 can also be matched. That is, a narrow reception beam each element 1 _i-12 ~1 _i + ₁₁ is by performing time axis conversion of the signals received, under the elements 1 _i-12 ~1 _i + _11, the focus is continuously seamlessly Can be formed. This received beam can be said to be a needle beam that is localized in a thin region centered on the alternate long and short dash line.

In the above description, the element used as a reference for time axis conversion is described as the element 1 _i-1 , but the element used as the reference may be any of 24 elements. However, if the time axis conversion is performed on the basis of the element closest to the focal point, the number of data after the time axis conversion can be minimized (the ultrasonic propagation time between the element and the focal point is the shortest). So there is a merit in device manufacturing.

More specifically, the time axis conversion is performed as follows. An element used as a reference for time axis conversion is an element 1 _i-1 , and this time axis is t. Then, the time axis t _i-12 of the element whose time axis is converted (for example, the element 1 _i-12 ) is expressed by t _i−12 = f _i−12 (t ) Can be written. At this time, the signal received by the element 1 _i-12 is expressed as A _i-12 (t _i-12 ) when its amplitude is expressed by a function A. Therefore, the operation of time axis conversion is nothing but finding A _i-12 (t), and it can be written as A _i-12 (f ^-1 _i-12 (t _i-12 )) using an inverse function. it can. A time axis conversion relationship necessary for this operation is given to the time axis conversion unit 11 from the setting unit 21 in advance. The signal handled here is digital data, and the number of data of the element closest to the focal point is the smallest (the propagation distance of the ultrasonic wave is short). In the time axis conversion, processing for reducing the number of data is performed. In order to reduce the number of data, it is advisable to perform a thinning process that is devised so that data with a large amplitude is not lost.

FIG. 1 shows a simplified configuration in which one receiving needle beam localized in a narrow region corresponding to the beam focusing size centered on the one-dot chain line is formed. Waves are received and A / D converted so that a receiving needle beam having a continuous focal point can be formed between the distances F _{RS to} F _RE below the elements 1 _i-12 to 1 _{i + 11} of the transducer array. A time axis conversion unit 11 that performs time axis conversion of the signal is provided.

The specific operation is as follows. Ultrasonic waves are transmitted from all the elements 1 ₁ to 1 _{384 of the} transducer array 1. In addition, an ultrasonic reflection signal (echo) from the subject is received using all the elements ₁₁ to ₃₈₄ of the transducer array 1. The ultrasonic signals received by the elements 1 _i-12 to 1 _{i + 11} are amplified by the receiving amplifiers 3 _{i-12 to} 3 _{i + 11} , respectively, and then delayed elements 4 _i-12 to 4 _{i. +11} delayed in units (4 elements in the figure) more elements by, after being summed combined by summing combiner _{5 i-12 ~5 i + 8} ( subscript in FIG shaped four intervals), a / D converter The digital signals are converted by the devices 6 _{i-12 to} 6 _{i + 8} (in the figure, subscripts are every fourth). The time axis conversion units 11 _{i-12 to} 11 _{i + 8} (in the figure, subscripts are every fourth) are calculated in advance in the setting unit 21 so as to set the focal point continuously between the distances F _{RS to} F _RE. Based on the stored propagation time relative data, the time axis of the signal received by the elements other than the reference element is converted and sent to the waveform memories 12 _{i-12 to} 12 _{i + 11} . The signal of the element used as a reference is sent as it is. In FIG. 1, since four elements of superimposed signals are input to one time axis conversion unit 11 _{i-12 to} 11 _{i + 8} , the one time axis conversion unit performs time axis conversion for four elements. Data is created and sent to the waveform memories 12 _{i-12 to} 12 _{i + 11} prepared for each element.

The signals recorded in the waveform memories 12 _{i−12 to} 12 _{i + 11} are sent to the addition / synthesis processing unit 13 to be added / synthesized. In this way, a signal received by the receiving needle beam having a continuous focal point formed between the distances F _{RS to} F _RE is obtained.

FIG. 4 shows a configuration in which the receiving needle beam curtain is formed by simultaneously arranging the receiving needle beams below the elements of the transducer array 1. In this configuration, a total of 361 receiving needle beams are formed under the elements 1 _j to 1 _{j + 1} (j = 12, 13, 14,..., 370, 371, 372) of the transducer array 1. Is done. In FIG. 4, in order to avoid complication of the drawing, elements 1 _i-13 to 1 _{i + 10} , elements 1 _i-12 to 1 _{i + 11} , and elements 1 _i-11 to 1 _{i + 12} are respectively located below. It shows how a receiving needle beam is formed. The receiving needle beam formed by the elements 1 _i-13 to 1 _{i + 10} is NB _i-1 , the receiving needle beam formed by the elements 1 _i-12 to 1 _{i + 11} is NB _i , and the element 1 _i- A receiving needle beam formed by ₁₁ to 1 _{i + 12} is denoted as NB _{i + 1} .

  The operations of the transducer array 1, the pulser 2, the receiving amplifier 3, the delay element 4, the adder / synthesizer 5, and the A / D converter 6 are the same as those already described with reference to FIG.

Since one element of the transducer array is used to form 24 receiving needle beams at the same time, it is necessary to store a total of 24 time-axis converted signals in a waveform memory connected to each element. Therefore, the waveform memories 12 ₁ to 12 ₃₈₄ is divided into 24 regions.

The time axis conversion unit 11 for sending the signal subjected to time axis conversion to the waveform memory 12 converts 24 time axes from the received signal according to the distance between each element and the positions where the 24 received needle beams are formed. The generated signal is generated and sent to the waveform memory 12. In order to obtain, for example, a received signal by the received needle beam NB _i-1 from the received signal recorded in the waveform memory 12, the time axis conversion recorded in the waveform memories 12 _{i-13 to} 12 _{i + 10} is performed. Then, a signal subjected to time-axis conversion so as to form a receiving needle beam under the elements 1 _i-13 to 1 _{i + 10} is sent to the addition / synthesis processing unit 13 _i-1 . These signals are added and synthesized in the addition synthesis processing unit 13 _i-1 .

In this manner, a signal received by the receiving needle beam NB _i-1 formed between the distances F _{RS to} F _RE is obtained. Signals received by other receiving needle beams can be obtained using a similar process.

  In this embodiment, in order to avoid complication of explanation, the configuration in which the wave is received by the wave-receiving needle beam in one type of medium is shown. Needless to say, when there are two or more types of media such as a water immersion flaw detection of a metal material, refraction of ultrasonic waves is taken into consideration in the above-described calculation of distance.

  In the present embodiment, a method of forming a receiving needle beam having a continuous focal point under 24 elements has been described. This is an example, and any number of elements used for beam forming may be used as long as it is four or more.

  In general, the focusing range in the transmission direction of the received beam is increased according to the distance between the focal point and the transducer array. Therefore, it is preferable to determine the distance between the received beam focal points accordingly.

Note that the ultrasonic beam diameter d at the focal position is approximately expressed by equation (1).
d = λ · F / D (1)
Where λ is the wavelength of the ultrasonic wave, F is the focal length of the focused beam, D is the width of the grouped transducer (element pitch × number of elements)

  Accordingly, if the focal length F is increased while the transducer width D is kept constant, the beam diameter d increases, so that it is possible to change D so as to obtain a desired beam diameter according to the focal length F. . Specifically, the number of elements used for forming the receiving needle beam may be changed according to the focal length F.

  In the transmission, ultrasonic waves may be transmitted simultaneously from all elements of the transducer array 1, or by controlling the timing of applying an electrical pulse from the pulsar 2 to each element of the transducer array 1, The ultrasonic wave may be transmitted obliquely with respect to the normal line of the transducer array 1 or may be transmitted so as to be focused under the transducer array. In short, the transmission method may be selected so that an echo having a sufficient S / N can be obtained according to the shape of the internal defect to be detected.

  Here, the advantage of the present invention over Patent Document 2 will be described again.

(1) In Patent Document 2, a signal received by the transducer array is recorded in a two-dimensional memory, and the inside of the memory is scanned to form a received beam focus in the entire predetermined depth range. It was. On the other hand, in the present invention, as described below, the signal obtained by processing the received signal is stored in the memory so that it can be used as it is for forming the received beam focus. Therefore, it is necessary to scan the memory. The processing speed can be significantly increased.

  1) Immediately after A / D conversion of a signal necessary for receiving beam focus formation, it is previously extracted or time axis converted and stored in a memory.

  2) The signal stored in the memory is used only for addition processing, and the receiving beam focus is continuously formed in a desired direction.

(2) In Patent Document 2, the focus of a received beam is formed at a specific position by phase-combining all n received signals received by n elements. In this case, since a high percentage of transducers that do not contribute to receiving beam formation are included, not only is there a lot of waste in the calculation in phase synthesis, but it also causes generation of a noise signal with a large amplitude. In the present invention, since a small transducer group is selected from the transducer array 1 and the received beam focus is formed only by this transducer group, there is a problem of wasteful calculation and a large amplitude as in Patent Document 2. There is no problem of generation of noise signal.

  In order to verify the effectiveness of the present invention, FIG. 5 shows the detection of minute non-metallic inclusions in a thin steel plate having a thickness of 2 to 3 mm by vibration with a frequency of 50 MHz, an element pitch of 0.1 mm, and an element number of 384. The result performed using the child array is shown. In this experiment, the non-metallic inclusions were detected while the steel plate was conveyed using a transfer stage. Experiments were performed using the apparatus of the first and second embodiments as the apparatus of the present invention. For comparison, an apparatus capable of realizing the receiving focus forming method disclosed in Patent Document 2 was also prepared and tested. Further, for comparison with a general electronic scanning technique, an experiment using general linear electronic scanning (electronic scanning of a focused transmission / reception beam) was performed using the same transducer array. FIG. 5 shows a C-scope obtained in each experiment, which detects the amplitude of an echo signal from an internal defect and modulates the luminance according to the amplitude to display an internal defect image. The horizontal direction of the C-scope in FIG. 5 is the conveying direction of the steel plate. In general linear electronic scanning, when the focal length of the received focused beam is changed multiple times (experiments are carried out by transporting the steel sheet each time the focal length is changed), the clearest internal defect image is obtained ( C-scope of underwater focal length: 15 mm) is shown. The C-scope obtained by using the apparatus according to the present invention in FIG. 5 and the apparatus of Patent Document 2 is equivalent to a C-scope obtained by general linear electronic scanning. This is a C-scope obtained when a steel plate is conveyed at the maximum speed limit. In the case of the present invention, since substantially the same internal defect images were obtained with the apparatuses of the first and second embodiments, FIG. 5 shows a C-scope obtained using the apparatus of the second embodiment. Table 1 shows the maximum conveyance speed in the above experiment and the time required to visualize the region shown in FIG. However, in the case of general linear electronic scanning, the maximum steel plate conveyance speed and the required time at one focal length setting are shown. In order to thoroughly inspect the entire cross section of a steel sheet having a thickness of 2 to 3 mm, in the case of general linear electronic scanning, even if only the time required for detection is considered, the time is about 10 times the required time in Table 1. is required.

  Referring to the C-scope of FIG. 5 and Table 1, the apparatus according to the present invention is 10 to 100 times faster than the conventional apparatus (the apparatus of Patent Document 2, the apparatus based on general linear electronic scanning). It can be seen that even if the steel plate is conveyed, an internal defect image with almost no difference can be obtained. In the apparatus of Patent Document 2, since all the n received signals received by the n elements are phase-synthesized, a high percentage of transducers that do not contribute to receiving beam formation are included. Due to the periodic noise contained in the signal received by the vibrator that does not contribute to the formation, the noise level increased throughout the C-scope. FIG. 5 clearly shows the problem of the device of Patent Document 2 described above. The ultrasonic transmission / reception repetition of the apparatus according to the present invention is 10 kHz, whereas the ultrasonic transmission / reception repetition of the apparatus of Patent Document 2 is limited to 1 kHz as shown in Patent Document 2. It was. The apparatus according to the present invention can be advantageously applied to the examination of a subject transferred at high speed.

In the devices of the second and third embodiments, ultrasonic waves are transmitted and received from all the elements 1 ₁ to 1 ₃₈₄ of the transducer array 1, but it is also possible to transmit and receive ultrasonic waves using some elements. . Further, the total number of elements is not limited to 128 or 384.

The block diagram which shows the simplified structure of embodiment of the ultrasonic inspection apparatus for implementing this invention Explanatory drawing showing the concept of the present invention Explanatory drawing which shows the relative relationship of the time when an ultrasonic wave propagates between two specified elements and a focus The block diagram which shows the whole structure of embodiment of the ultrasonic inspection apparatus for implementing this invention The figure which compares and shows C-scope obtained by the apparatus of 3rd Embodiment, patent document 2, and the conventional linear electronic scanning. Block diagram showing the configuration of a conventional ultrasonic inspection apparatus

Explanation of symbols

1 ... transducer array 1 ₁ to 1 ₁₂₈ ... ultrasonic oscillators 21 _{to 128} ... pulsar 3 ₁ to 3 ₁₂₈ ... reception amplifier 41 _{to 128} ... delay elements 5 ₁ to 5 ₁₂₈ ... summing amplifier 6 ₁ 6 ₁₂₈ ... A / D converter 11 _{1 to} 11 ₁₂₈ ... time-axis conversion unit 12 _{1 to} 12 ₁₂₈ ... waveform memory 13 _{1 to} 13 ₃₈₄ ... addition synthesis processing unit

Claims (4)

When inspecting a cross section of a subject using a transducer array composed of a large number of ultrasonic transducers arranged one-dimensionally, ultrasonic waves are transmitted from a part or all of the transducers of the transducer array. The reflected wave generated by the transmitted ultrasonic wave is received using some or all of the ultrasonic transducers of the transducer array, and the received signal is converted into a digital waveform signal. Each transducer of the first ultrasound transducer group composed of a plurality of ultrasound transducers selected from the transducer array and a continuous receiving focus formed inside the subject. Based on the distance, the time axis of the digitized received signal of each transducer is converted, and the ultrasonic cross section inspection method for simultaneously adding and synthesizing the converted received signal of each transducer,
The transducer array is grouped into a group of ultrasonic transducers different from the first ultrasonic transducer group, each of which includes a plurality of ultrasonic transducers,
In each group, after adding different delays to multiple signals received by multiple ultrasonic transducers in the group,
A cross-sectional inspection method using ultrasonic waves, characterized in that a plurality of delayed signals are added to be combined into one signal.   2. The ultrasonic wave according to claim 1, wherein a plurality of first ultrasonic transducer groups each including a plurality of ultrasonic transducers are added, and addition and synthesis are simultaneously performed in the plurality of ultrasonic transducer groups. Cross section inspection method. An apparatus for inspecting a cross section of a subject using a transducer array composed of a large number of ultrasonic transducers arranged one-dimensionally, and transmitting ultrasonic waves from a part or all of the transducers of the transducer array Means for receiving reflected waves generated by the transmitted ultrasonic waves using a part or all of the ultrasonic transducers of the transducer array, and digitally converting the received signals. And a transducer formed in a first ultrasonic transducer group composed of a plurality of ultrasonic transducers selected from the transducer array and a continuous formed inside the subject. A means for converting the time axis of the digitized received signal of each transducer based on the distance to a typical received focus position, and a means for simultaneously adding and synthesizing the converted received signal of each transducer. An ultrasonic cross-section inspection apparatus provided,
Grouping the transducer array into a group of ultrasonic transducers different from the first ultrasonic transducer group, which is composed of a plurality of ultrasonic transducers,
In each group, delay means for adding different delays to a plurality of signals received by a plurality of ultrasonic transducers in the group,
Adding means for adding a plurality of delayed signals into one signal;
A cross-sectional inspection apparatus using ultrasonic waves, comprising:   The ultrasonic cross-sectional inspection apparatus according to claim 3, wherein the adding and synthesizing unit simultaneously performs addition and synthesis in the plurality of first ultrasonic transducer groups.