JPS62150158A - Array probe for spatial scanning - Google Patents

Abstract

PURPOSE:To enable efficient transmission and reception of ultrasonic wave, by mounting shoes fit on the rim of an array probe having a reflection surface vertical to an ultrasonic wave transmitting surface of the array probe with a plurality of ultrasonic transmitting/receiving elements arranged to utilize the reflection of the reflection surface. CONSTITUTION:An ultrasonic wave reflection surface 3 is set vertical to an ultrasonic transmission surface fit on the rim thereof 1 with a sound pressure reflectance gamma of -1. A primary grating lobe 7 propagates through an object 4 being inspected but -1 primary grating lobe 8 is reflected with the ultrasonic wave reflection surface 3 to be propagating in the same direction as the primary grating lobe 7. At this point, as the reflected grating lobe 8 thus reflected is the same in the phase as the primary grating lobe, both intensify each other to form a synthesized ultrasonic wave 12. This provides a sound pressure the same as would be obtained with the existence of array probe 1; doubling in the size. It will be an ultrasonic distribution only in the direction. To be termed simply, the array element for reverse phase transmission is expressed by symbol -while the array element for normal phase transmission by symbol +. Thus, a higher SN ratio is possible with a higher transmitting/receiving efficiency.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an array probe used for ultrasonic measurements such as ultrasonic flaw detection, and in particular to an array probe suitable for ultrasonic beam control using spatial switching scanning. related to array probes for use.

[Conventional technology]

To control the incident angle of an ultrasound beam without using a delay element, for example, each element of an array probe is selected at equal intervals, and ultrasound is transmitted simultaneously from each element to prevent interference between the transmitted waves. There is a method that utilizes ±n-order grating lobes generated by . However, in this case, in addition to the grating lobes, a vertical beam is also generated, which interferes with oblique flaw detection, and it is necessary to remove the vertical beam. Therefore, an array element in the middle of the array elements selected at equal intervals is further selected and transmitted simultaneously with the opposite phase to the selected element, and as a result of the interference of the ultrasonic waves from each of these array elements, a vertical beam and an even-order beam are generated. There is a method that can remove grating lobes. Even in this case, grating lobes are generated symmetrically with respect to the direction perpendicular to the surface of the probe, so in order to identify the position of the ultrasound reflection source, two probes are used to transmit and receive ultrasound separately. There is a drawback that the above-mentioned ultrasonic transmission/reception method cannot be applied in cases where the two-probe method cannot be used, such as in narrow spaces.

[Problem that the invention seeks to solve]

There are two ways to use an array probe to control the angle of incidence to change the propagation direction of an ultrasound beam: a method that uses a delay circuit, and a method that selects array elements at equal intervals and simultaneously transmits ultrasound from them. be.

The former has the disadvantage that the delay element is expensive, so the device itself is expensive, while the latter uses grating lobes that are generated symmetrically on the array probe, so it is necessary to use two separate transmitters and receivers to locate the defect location. A probe method is required, making it unsuitable for inspecting narrow spaces. Since the former disadvantage is an unavoidable problem at present, the latter disadvantage will be described below.

Here, the latter ultrasonic beam control method is referred to as a spatial scanning method. In the spatial scanning method, each element of the array probe is selected at equal intervals and ultralong waves are transmitted at the same time, so due to structural symmetry, grating lobes in the θ direction and grating lobes in the 10 directions are generated at the same time. Therefore, when grating lobes are used for ultrasonic flaw detection, it is impossible to determine whether the reflected waves are from the θ direction or the −〇 direction.
Separate array probes must be used to transmit and receive ultrasound. The present invention combines the grating lobes propagating in the two directions described above into one, and enables ultrasonic flaw detection with one array probe.

[Means for solving problems]

The above problem was solved by attaching a shoe to the array probe that converts the grating lobes that propagate in two directions into grating lobes that propagate in one direction through end face reflection using the spatial scanning method using the array probe. can.

[Effect]

Of the two grating lobes symmetrically transmitted from the array probe, the grating lobe that cannot be used for flaw detection can be used for flaw detection by reflection. Therefore, the ultrasonic transmission/reception efficiency and the S/N ratio can be improved, and ultrasonic flaw detection can be performed using one array probe.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
FIG. 1 is a side view showing the structure of a spatial scanning array probe according to the present invention. The shoe 2 that propagates the ultrasonic waves 5 from the array probe 1 to the subject 4 is made of acrylic or the like, and a mirror-like ultrasonic reflection surface 3 that reflects the ultrasonic waves is used on one end surface of this shoe. It has characteristics. Generally, the sound pressure repulsion coefficient γ of ultrasonic waves is expressed by equation (1).

Here, Z is the acoustic impedance of the incident medium, Z2
is the acoustic impedance of the reflecting medium.

Therefore, in FIG. 1, if 71 is the acoustic impedance of the shoe 2 and Z2 is the acoustic impedance in the air, generally 21>2. Therefore, the sound pressure reflectance γ at this time is given by the following equation.

γ Valve-1 (2) Therefore, all the ultrasonic waves incident on the ultrasonic reflecting surface 3 are reflected. However, the phase of the sound pressure is opposite to that of the incident wave.

Figure 2 shows the principle of controlling the incident angle of an ultrasonic beam using the spatial scanning method. When array elements 10 are selected at equal intervals from the array probe 1 and ultrasonic waves are simultaneously transmitted by the ultrasonic transmitter/receiver 9, a ±1st-order grating lobe 7.8 is generated that propagates in the ±0 direction according to the following formula. .

θ=±5in-' () ・・・・・・・・・・・・
(3) Here, λ is the ultrasonic waves 6, 7 propagating through the object 4
The wavelength is 8°, and d is the spacing between the selected array elements 10. In this case, in addition to the grating lobes 7.8 that propagate in the ±θ force direction, there is a main lobe 6 that propagates perpendicularly from the array probe 1, which is not preferable because it acts as a noise source during oblique ultrasonic flaw detection. Therefore, a method shown in FIG. 3 was devised as a method of canceling out this main lobe 6.

FIG. 3 shows that the elements 11 between the array elements 10 selected from the array probe 1 in FIG. Ultrasonic waves are transmitted in an opposite phase from an ultrasonic transmitter/receiver 9' having an opposite phase to the ultrasonic transmitter/receiver 9. As a result,
These two types of waves interfere with each other, canceling out the main lobe 6, and furthermore, the effect of doubling the sound pressure of the ±1st-order grating lobe 7.8 can be obtained. However, since there are ultrasonic waves in two directions with ±1st-order grating lobes7.8, when this method is used for ultrasonic flaw detection, two probes that transmit and receive separately are required to locate the defect location. A child law is required.

Therefore, it is unsuitable for inspecting narrow spaces, etc.''2.It also has the disadvantage that it requires twice as many ultrasonic transmitters and receivers compared to the single probe method. Therefore, by using equation (1), we devised an array probe that can perform the -probe method.

FIG. 4 is a diagram showing the basic principle of the present invention. In this case, the ultrasonic reflecting surface 3 is set perpendicular to the ultrasonic transmitting surface of the array probe 1 in line with the edge of the array probe 1.
The sound pressure reflectance γ is set to −1. The first-order grating lobe 7 propagates through the object 4 as it is, but the -1st-order grating lobe 8 is reflected by the ultrasound reflecting surface 3 and propagates in the same direction as the first-order grating lobe 7. Ru. At this time, since the reflected grating lobe 8 is in the same phase as the first-order grating lobe, both of them strengthen each other and become a combined ultrasonic wave 12.

Therefore, a sound pressure distribution similar to that obtained when the array probe 1' of twice the size is present is obtained, and the ultrasonic wave distribution is only in the θ direction. For the sake of simplicity, including FIG. 4, the array element 11 for anti-phase transmission is indicated by one symbol, and the array element 10 for positive-phase transmission is indicated by a ten symbol. A method specifically illustrating this is the embodiment shown in FIG.

Several other examples are shown below. Figure 5(a).

(b) Sound pressure reflection of ultrasonic reflecting surface γ; 0 (lγ1 × 1)
This is an example in which the array probe 1 is installed with respect to the ultrasonic reflecting surface 3.

FIG. 5(a) shows the case where γ is O, and the position of the ultrasonic reflecting surface 3 needs to match the edge of the array probe.

FIG. 5(b) shows the case where γ>0, and the position of the ultrasonic reflecting surface 3 must be at the center of the array element 10 at the edge of the array probe 1. These are necessary because the reflected first-order grating lobe 8 interferes with the first-order grating lobe, increasing the sound pressure amplitude. If these conditions cannot be obtained, both superfluous This is because sound waves tend to cancel each other out.

Another embodiment is shown in FIGS. 6(a) and 6(b). For some reason, this is shown in FIG. 5(a).

This is a case where the condition shown in (b) cannot be satisfied.

FIG. 3 is a diagram showing conditions when the ultrasonic reflecting surface 3 and the edge of the array probe 1 cannot be placed close to each other. When the length of the array element 10 is P, np for γ 0, and (n +
-) This indicates that it is sufficient to install the devices at a distance of p. (n:
(Integer) Note that from Fig. 1 to Fig. 6, for the sake of simplicity, every other array element 1 transmits in positive phase and anti-phase, but between the elements selected by formula (3), Since the number of objects can be changed, the results may not always be as shown in FIGS. 1 to 6.

Furthermore, the same method can be used not only when the ultrasonic reflecting surface is composed of only the shoe 2 and air, but also when the acoustic impedance is significantly different from that of the shoe 2 instead of air.

〔Effect of the invention〕

According to the present invention, grating lobes for oblique deep scratches using a spatial scanning method can be propagated only in one direction,
Not only is it possible to detect defects in narrow spaces by transmitting and receiving ultrasonic waves using a single array probe, but also the signal-to-noise ratio can be improved because the transmission and reception efficiency is nearly doubled.

[Brief explanation of drawings]

Fig. 1 is a side view showing the structure of the spatial scanning array probe according to the present invention, Fig. 2 is a side view showing ultrasonic beam control using the spatial scanning method, and Fig. 3 is a side view showing the main lobe control in the spatial scanning method. FIG. 4 is a side view showing the erasing method, FIG. 4 is a side view showing the basic principle of the present invention, FIGS. 5(a), (b), and FIG. 6(a). (b) is a side view showing an embodiment of the spatial scanning array probe of the present invention. 1... Array probe, 1'... Double length array probe, 2... Shoe, 3... Ultrasonic reflecting surface, 4... Subject, 5... Ultrasonic wave , 6... Main lobe, 7...
・First-order grating lobe, 8... First-order grating lobe, 9... Ultrasonic transceiver (positive phase),
9'... Ultrasonic transmitter/receiver (opposite phase), 10... Array element (positive phase), 11... Array element (opposite phase), 1
2...Synthetic ultrasound.

Claims (1)

[Claims] 1. In an array probe with multiple ultrasonic transmitting/receiving elements lined up, a shoe with a reflective surface perpendicular to the ultrasonic transmitting surface of the array probe aligned with the edge of the array probe is installed to reduce the reflection. A spatial scanning array probe that is characterized by its ability to efficiently transmit and receive ultrasonic waves using surface reflection.