JP2683719B2 - Ultrasound imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention scans a subject with a plurality of ultrasonic beams to obtain an acoustic image that two-dimensionally shows the state of the surface of the subject and the vicinity thereof. The present invention relates to an ultrasonic imaging device. (Prior Art) Recently, there has been great interest in non-destructive inspection technology. Among them, the one using ultrasonic technology is a powerful tool for displaying the internal state of an optically opaque substance. Is attracting attention as a means. In the ultrasonic technology, it is known that a transducer capable of transmitting and receiving a Lamb wave can be configured by providing a thin plate-like piezoelectric comb-shaped electrode. Such a transducer effectively functions as an in-liquid ultrasonic transducer by being arranged and driven on the boundary surface with the liquid. Conventionally, as an ultrasonic device of this type, for example, JP-A-58-
Some were disclosed in Japanese Patent No. 22978. FIG. 2 shows such an ultrasonic device. That is, on one plane of the piezoelectric plate 1, transducers T _in and T
_Out is arranged in the form of dividing one circle into two. The transducers T _in and T _out each have a pair of interdigital electrodes Ea, Eb; Ec, Ed arranged on a concentric circle. The transducer T _in functions as an electrode that transmits an ultrasonic beam, and the transducer T _out functions as an electrode that receives a reflected wave of the ultrasonic beam. The piezoelectric plate 1 has a third structure in order to function as an ultrasonic device.
As shown in the drawing, the surface provided with the transducer T _in is placed so as to be immersed in the liquid L (for example, pure water). Further, the subject 2 is placed at a position in the liquid facing the piezoelectric plate 1. To the interdigital electrodes Ea and Eb of the transducer T _in , an electric signal S _i in the radio frequency range, which is determined by the piezoelectric plate 1 and the electrode period, is applied from a signal source (not shown). Thus, as shown by the arrows in FIG. 3, the angle theta ₁ towards the transducer T _in the subject _2, θ 2 ₍₀
<Θ ₁ <90 °, 0 <θ ₂ <90 °), and a longitudinal ultrasonic wave beam is emitted to the liquid L. This ultrasonic beam is the liquid L
Propagates through and reaches the subject 2, a part of which is reflected by the surface of the subject 2 (dotted line), and the other proceeds inside and is reflected (solid line). The reflected longitudinal ultrasonic wave beam is again incident on the transducer T _out via the liquid L and is converted into an electric signal S _o . As long as the reflection point and its vicinity are not elastically anisotropic, the transducers T _in and T _out have a confocal point on the central axis of the circle, so they are detected by the transducer T _out ,
It is taken out as an electric signal S _o . If the transmission medium of the ultrasonic beam is homogeneous, the electric signal S _o has a form in which the electric signal S _i is delayed, but the surface of the subject 2 irradiated by the ultrasonic beam and the inside thereof are elastically nonuniform. When sex exists,
A change occurs in the propagation velocity of the sound wave, and the amplitude and phase difference correspondingly change. Therefore, when the signal analysis is performed on the electric signal S _o having such an amplitude and a phase difference, it is possible to detect the surface and internal states of the subject 2, for example, the surface of the subject and cracks in the vicinity thereof. (Problems to be Solved by the Invention) However, according to the ultrasonic device having such a configuration, there is only one transducer for transmitting and receiving the ultrasonic beam, and therefore, the resolution in the propagation direction of the sound wave is smaller than that in the azimuth direction. There was a problem that it was inferior. The present invention has been made for the purpose of solving the problems that the above-mentioned conventional techniques have.
It is an object of the present invention to provide an ultrasonic imaging apparatus capable of obtaining data required for two-dimensional display with improved resolution in both distance and azimuth directions. (Means for Solving the Problems) An ultrasonic imaging apparatus according to the present invention includes an ultrasonic beam transmitting transducer and a receiving transducer, which are arranged on a piezoelectric plate, respectively, and receives the ultrasonic beam of the transmitting transducer. In a device in which an ultrasonic beam emitted from a specimen and reflected from the subject is received by a receiving transducer to obtain a detection signal indicating the state of the subject, the transmitting transducer and the receiving transducer are the same piezoelectric substrate. Are interdigital transducers in the shape of arcs that form concentric circles on the same plane, and are provided in pairs so as to transmit and receive ultrasonic beams that are orthogonal to each other. Further, this ultrasonic imaging apparatus detects, from a moving means for moving an object to scan it with an ultrasonic beam and a series of detection signals obtained by this scanning, a detection corresponding to mutually orthogonal ultrasonic beams of the object. And a data processing unit for generating an acoustic image signal with improved distance resolution by obtaining signals or multiplying or summing detection signals corresponding to the obtained orthogonal ultrasonic beams. (Operation) Since the transducers are arc-shaped interdigital transducers that form concentric circles on the same plane of the same piezoelectric substrate, multiple pairs of transmitting and receiving transducers are acoustically independent and are orthogonal to each other. The manufacturing process is greatly facilitated when provision is made for transmitting and receiving acoustic beams. That is, by using the arc-shaped interdigital transducer having such a configuration, each transducer capable of reliably transmitting and receiving orthogonal ultrasonic beams can be manufactured easily and accurately for the first time. In the interdigital transducer, the overlapping portion of the interdigital transducer effectively functions as a transducer for emitting and receiving the ultrasonic beam, and the emitting and receiving directions of the ultrasonic beam are perpendicular to the interdigital electrode. . Therefore, the desired transducer can be made extremely easy simply by forming concentric circular arcs on the same plane of the same piezoelectric substrate and forming the angle of the interdigital transducer fingers of each transducer so that the emitting direction and the receiving direction are orthogonal to each other. It can be manufactured with high accuracy. What is particularly important in the present invention is to obtain detection signals corresponding to mutually orthogonal ultrasonic beams of a subject, and obtain the product or sum of the detected signals corresponding to the mutually orthogonal ultrasonic beams. To generate a signal. Since a good azimuth resolution can be obtained in each azimuth, the resolution (distance resolution) in the traveling direction of the ultrasonic beam can be significantly improved by taking the product or sum of the detection signals in the azimuth directions. You can Moreover, the signal processing therefor is extremely simplified. (Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. The piezoelectric plate 1 is made of, for example, a piezoelectric ceramic sold under the trade name of NEPEC-6, and has a diameter of 14 mm and a thickness of 220 mm.
μm. Four interdigital transducers 1a, 1b, 1c and 1d functioning as ultrasonic transducers are formed on one flat surface (lower surface in the figure) of the piezoelectric plate 1. The interdigital electrodes 1a, 1b, 1c and 1d are arranged in a form of dividing one circle into four, and have an electrode length of 430 μm and 2.5 pairs. The interdigital electrodes 1a and 1b are driven by an electric signal S _i supplied from a circuit (not shown), and function as transmitting electrodes for ultrasonic beams. Also, the interdigital electrode 1c,
1d is connected to the circuit described below and functions as a receiving electrode for the ultrasonic beam. The ultrasonic beams emitted from the interdigital transducers 1a and 1b are emitted via the liquid L to the subject 2 arranged near the convergence point thereof, as shown in FIG. 4b. For convenience of explanation, the subject 2 is, as shown in FIG.
Two types are prepared. The subject 2 shown in FIG. 5 has a vertical x of 40.
mm, width y is 30 mm, thickness d is 1 mm, and the bottom surface is provided with grid-like grooves that are etched in a grid pattern at intervals w of 1 mm. The width of the groove is about 250 μm. Depth is about 1
00 μm. The ultrasonic beams reflected by the subject 2 are incident on the corresponding interdigital transducers 1c and 1d to generate an electrical signal.
Converted to S _o1 , S _o2 . The signals S _o1 and S _o2 are input to the detection circuit 3. The detection circuit 3 is connected to the gate signal generator 4 and has an analog switch (not shown) that is opened / closed by the gate signal 4a input from the gate signal generator 4. By opening and closing this analog switch, the signals S _o1 and S _o2 are gated, and the analog-digital converter (AD
C) is supplied to 5. The analog / digital converter 5 includes a computer (CPU) 7 as data processing means, a display device (CRT) 8, a printer (PRN) 9, and a subject 2 for scanning the subject 2 via a bus 6. A motor drive circuit 10 as moving means for driving a motor (not shown) provided for moving the
It is connected to an external storage device 11 that stores data of the computer 7. Next, the operation will be described. FIG. 4 is a layout diagram showing the positional correspondence between the piezoelectric plate 1 and the subject 2 shown in FIG. FIG. 4b shows the piezoelectric plate 1 shown in FIG.
FIG. 4c shows the state of the subject 2 cut along the line X '.
Shows the state of cutting at the same position. Interdigital transducer 1a,
The ultrasonic beam emitted from 1b reaches the subject 2 through the liquid L at an angle θ as shown in FIG. 4b. A part of the subject 2 is directly reflected on the surface of the subject 2, and the other part of the subject 2 travels inside and is reflected. Here, the ultrasonic beam of the interdigital transducer 1a and the ultrasonic beam of the interdigital electrode 1b are orthogonal to each other, but if the subject 2 does not have elastic anisotropy due to scratches, etc. There is no phase difference. However, when the subject 2 has elastic anisotropy due to scratches or the like, the reflected interdigital electrodes are reflected.
A phase difference appears in the ultrasonic beams 1a and 1b. The signals S _o1 and S _o2 of the interdigital transducers 1c and 1d are input to the detection circuit 3. Since the signals S _o1 and S _o2 include unnecessary reflected wave components generated in the propagation path,
The detection circuit 3 extracts a certain signal component from the signals S _o1 and S _o2 as shown in FIG. 6b by the gate signal 4a, and inputs it as the signal 3a to the analog / digital converter 5. The analog / digital converter 5 converts the signal 3a from the detection circuit 3 into a digital signal. The computer 7 stores this signal in the external storage device 11 as detection data. Hereinafter, by controlling the motor drive circuit 10, the subject 2 is moved stepwise in the XY directions, and by repeating such a series of operations, the subject 2 is subjected to ultrasonic beams from the interdigital electrodes 1a and 1b. To scan. The computer 7 performs image processing using the series of detection data thus stored in the external storage device 11,
The acoustic image as shown in the figure is displayed on the display screen of the display device 8 or is output by the printer 9. FIG. 7a is an acoustic image diagram represented by an acoustic image signal generated from a detection signal obtained by scanning the subject 2 shown in FIG. 5 on the side without grid (the lower side of the figure) with an ultrasonic beam. . In this case, the scanning interval, that is, the movement step is 10
0 μm. The line XX 'shown in FIG. 1 indicates the interdigital transducer 1
This is the case where an ultrasonic beam is propagated from the a to the interdigital transducer 1c, which is called the X mode. YY 'is a case where an ultrasonic mode is propagated from the interdigital electrode 1b to the interdigital electrode 1d, which is called the Y mode. Interdigital electrode
1c and 1d convert the ultrasonic beam incident through the path in the direction of the arrow shown in the figure into an electric signal and output it. Since the detection signal obtained in the X mode or the Y mode is obtained by one ultrasonic beam, the azimuth resolution is excellent, but the distance resolution has a problem. However, by taking the product or sum of the detection signals obtained in X mode or Y mode,
It is possible to solve such a problem. For example,
FIG. 7a is an acoustic image diagram in which the detection signals obtained in the X mode and the Y mode are superimposed, that is, the sum is shown. FIG. 7b is an acoustic image diagram showing the product of the detection signals obtained in the X mode and the Y mode. (Effect of the Invention) As described in detail above, according to the present invention, the transmitting transducer and the receiving transducer are arc-shaped interdigital transducers that form concentric circles on the same plane of the same piezoelectric substrate, and The ultrasonic imaging apparatus is provided with a plurality of pairs so as to transmit and receive orthogonal ultrasonic beams, and the ultrasonic imaging apparatus further includes moving means for moving the subject to scan with the ultrasonic beams, and the scanning means. From the series of detected signals, the detection signals corresponding to the mutually orthogonal ultrasonic beams of the subject are respectively obtained, and the distance resolution is obtained by taking the product or the sum of the obtained detection signals corresponding to the mutually orthogonal ultrasonic beams. With the data processing means for generating the improved acoustic image signal, it is possible to reliably transmit and receive orthogonal ultrasonic beams. Each transducer can be manufactured easily and accurately. Moreover, since the acoustic image signal is generated by taking the product or sum of the detection signals corresponding to the ultrasonic beams orthogonal to each other, the resolution (distance resolution) in the traveling direction of the ultrasonic beam for the subject is greatly improved. A two-dimensional image can be obtained. Moreover, the signal processing for that is greatly simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an ultrasonic imaging apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of a conventional ultrasonic apparatus, and FIG. Path diagram of sound beam, 4th
1 is a layout view of the piezoelectric plate and the subject of FIG. 1, FIG. 5 is a perspective view showing the shape of the subject, FIG. 6 is a waveform diagram of a signal input to a detection circuit, and FIG. 7 is according to the present invention. It is an acoustic image figure. 1 ... Piezoelectric plate, 1a, 1b, 1c, 1d ... Interdigital electrode, 3 ... Detection circuit, 5 ... Analog / digital converter, 7 ... Computer, 10 ... Motor drive circuit.

Claims (1)

(57) [Claims] Equipped with an ultrasonic beam transmitting transducer and an ultrasonic beam transmitting transducer respectively disposed on a piezoelectric plate, the ultrasonic beam of the transmitting transducer is emitted to a subject, and the ultrasonic beam reflected from the subject is received. In an ultrasonic imaging apparatus configured to receive a detection signal representing the state of the subject by receiving a transducer for transmission, the transmission transducer and the reception transducer form a concentric circle on the same plane of the same piezoelectric substrate. A plurality of arc-shaped interdigital transducers are provided in pairs so as to transmit and receive ultrasonic beams orthogonal to each other, the ultrasonic imaging apparatus, in order to scan the subject with the ultrasonic beam. From moving means for moving and a series of detection signals obtained by the scanning,
An acoustic image having improved distance resolution by obtaining detection signals corresponding to mutually orthogonal ultrasonic beams of the subject, and taking the product or sum of the obtained detection signals corresponding to mutually orthogonal ultrasonic beams. An ultrasonic imaging apparatus, comprising: a data processing unit that generates a signal.