JP2772647B2 - Ultrasound imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image apparatus capable of detecting an object located at a distant place by ultrasonic waves and displaying the object as a visible image.

[Conventional technology]

As means for detecting an underwater object, an underwater television using visible light, a sonar using a sound wave, a fish finder, and the like have been conventionally used. Among them, the underwater television has the excellent property that it is possible to accurately capture the shape, color, etc., but in normal transparency seawater, the short distance up to about 5 to 10 m is the detectable distance, Moreover, there is a problem that if the water becomes turbid, it becomes useless at all. Sonar and fish finder can detect a long distance of about 100m or more. However, on the other hand, there is a problem that the resolution of the image is poor and the shape of the object cannot be accurately captured.

On the other hand, 3D holographic image sonar using ultrasonic waves has the feature that it can detect the shape of an object with high resolution at a distance of 5 to 10 m to several 100 m. Is under development.

A conventional transmitting / receiving array is a one-dimensional array composed of a plurality of directional transmitters arranged side by side and linearly with respect to a target direction, and a one-dimensional array composed of a plurality of receivers similarly. A cross array in which a dimensional array and a cross were orthogonal was used.

The transmitter transmits the ultrasonic waves with the phases shifted one by one or several groups so as to converge at the target point (focal point) toward the target object, and transmits the ultrasonic waves with different phases. A video signal can be obtained by receiving the ultrasonic echo of the above by the receiver. Then, by scanning each target point in the target area, a video signal of a stereoscopic video can be obtained.

[Problems to be solved by the invention]

By the way, the time from the time of transmission in each scanning direction to the reception of the wave from the received signal, that is, the delay time is obtained, and the azimuth, distance and reflection intensity of the reflection point can be known from this data. The electronic circuit used for performing these calculations becomes complicated, and the next transmission cannot be performed until the echo of the transmitted sound wave is received. There is a problem in that a series of measurements for obtaining a two-dimensional image takes time. An example of the conventional method described above is as follows. At a transmission frequency of 300 kHz in a case of an electronic focusing method using a cross linear array (array size: φ400 mm) using 48 transducers and 64 transducers, the visual distance is about 100 m and the image reconstruction calculation time was 3 seconds (excluding the measurement time required for data collection).

The present invention has been made by focusing on the above problems, and enables stereoscopic image processing, a wide field of view, a longer viewing distance than before, and a measurement time (transmission-reception time). It is an object of the present invention to provide an ultrasonic imaging apparatus which can shorten the time required for image reproduction, shorten the image reproduction time and enable high-speed processing, and further reduce the size of the transmitting / receiving array and the signal processing device.

[Means for solving the problem]

In order to achieve the above object, the configuration of the ultrasonic imaging apparatus according to the present invention includes a plurality of omnidirectional ultrasonic transmitters and receivers, each on a plane intersecting the transmitting direction and the receiving direction. , Two-dimensionally arranged transmitting and receiving arrays are provided,
Orthogonal function generating means for generating a group of mutually orthogonal pulse waves, corresponding to the orthogonal function group obtained by changing the parameters of the orthogonal function formula consisting of Walsh functions for each transmitter, A modulating means for phase-modulating a transmitting carrier by a modulating pulse wave, and simultaneously transmitting an ultrasonic pulse transmitting signal provided from the modulating means from the transmitter, and a reflected wave of the transmitting pulse signal from an object. After receiving the received signals simultaneously by the plurality of receivers and obtaining the received signals, the transmission and reception of the ultrasonic signal which repeats the transmission and reception in the same manner.
The receiving means and the signal received for each receiver are subjected to correlation detection using the transmission signal of each transmitter, separated into signals for each receiver, and the separated signals are received by each receiver. Calculating means for determining a reflection position and a reflection intensity at the position from the wave time delay and the signal intensity, and calculating a spatial distribution of a sound field reflected from the total received signal; and the sound field intensity obtained by the calculation means Is provided with an image processing means for displaying the spatial distribution of the image on the image display device.

The form in which the transmitter and the receiver are two-dimensionally dispersed is not particularly limited. In a preferred form, the transmitting and receiving elements are arranged at equal intervals in a circular shape, and the transmitting array and the receiving array are disposed substantially concentrically, in a direction substantially perpendicular to the arrangement surface of the transmitting and receiving elements. Is made to coincide with the detection direction, and the transmitter array and the receiver array are on the same plane, which is advantageous in arithmetic processing.

Since the transmitter and the receiver of the present invention both use omnidirectional elements, there is no need to scan the target area with an ultrasonic beam as in the related art. The omni-directional transmission is transmitted so that the amplitude and phase characteristics can be regarded as constant in any direction, and having appropriate attenuation characteristics outside the field of view prevents noise from being generated by unnecessary signals. Desirable above.

The viewing angle is determined by the directional angles of the individual elements that make up the array. Generally, if an omnidirectional transmitting element is used,
It can cover up to 180 ° field of view. One feature of the present invention is that a wide field of view can be obtained with a small number of transmitting / receiving elements as described above.

The modulation by the orthogonal function is performed so that it is possible to identify from which transmitter the received reflected wave is a wave started. The modulation modulates the phase of the fundamental wave.Usually, the ultrasonic wave is divided into a plurality of wave numbers, for example, every 2 to 10 periods, and the phase of each wave number is shifted by 0 ° or 180 °. Modulate. By giving characteristics to this modulation pattern, it is possible to give characteristics to the transmission of each transmitter.

To modulate the phase as described above, Walsh (wa
lsh) It can be modulated by a phase inverter using a binary orthogonal function consisting of a function. The orthogonal function is wals
It can be obtained by changing the parameters of the h function.

Each of the receivers receives a superimposed reflected wave simultaneously transmitted from each transmitter. This can be separated by correlation detection using a signal from each transmitter by computer processing. The detection output includes information on the time until reception for each transmitter, and the distance and direction to the object can be known from this. Further, the time difference between the signals received by the respective receivers also includes information on the propagation direction of the reflected wave. Thus, the detection area can be visualized.

Therefore, even if the transmission signals transmitted simultaneously from a plurality of transmitters are waves reflected at different reflection points, they can be identified as different reflection points as long as their modulation contents can be separated and identified. In the case of the present invention, a carrier wave of 300 kHz is used, a Walsh function in which two periods of the carrier wave is a time width of one clock is used for modulation, and the diameter of the array is further reduced by 100 mm.
When the distance is 0 mm, it is possible to use a personal computer to identify an object at a distance of about 50 m in water and about 5 mm in the distance direction and about 80 mm in the angle direction.

[Action]

Since the omni-directional transmitter and receiver are used, it is not necessary to focus on the detection target or scan the detection area with an ultrasonic beam, and high-speed scanning, that is, information can be collected at high speed. To

The plurality of receivers can simultaneously acquire data in the detection area, and furthermore, it is possible to identify from which transmitter the signal originated by characterization using an orthogonal function. Since the reflected waves simultaneously received from different positions can be identified by the signals transmitted simultaneously from the wave elements, it is possible to detect each reflection point position in the detection area by one transmission.

Therefore, complicated operations such as focusing the measurement point by the ultrasonic beam and scanning the detection area are not required, and the apparatus can be simplified.

Also, from the received signal, a reflection signal from the same reflection point is selected, an operation for reproducing the reflected wave is performed, and an operation for reversing the reflected wave is performed using a computer without using an analog electronic circuit. As a result, the position of each reflection point can be obtained, so that the range of hardware processing can be reduced. Moreover, since the processing can be performed by a microcomputer-scale arithmetic device, it is possible to increase the speed by developing software even with the same device.

〔Example〕

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

FIG. 1 is a front view of an omnidirectional transmitting / receiving array used in this embodiment. That is, in this embodiment, the omnidirectional transmitter 1m
(M = 1~16) 16 pieces used as, on the substrate 2, and the transducer array 1 ₀ and at regular intervals so as to transmit in the forward direction of the substrate 2 and arranged in a circle. Also, the receiver 4 _n (n = 1 to 8)
As was eight used, the outer concentric transducer array 1 ₀ on the substrate 2, and the receiving array element 4 ₀ arranged at regular intervals to receive sound waves from the front direction of the substrate 2, the present embodiment Sending
The receiving array 5 was obtained. The outer diameter of the transmitting / receiving array used in this embodiment is about 12 cm for the transmitting array and about 12 cm for the receiving array.
The size was as small as 18 cm.

The block diagram shown in FIG. 2 is a schematic explanatory diagram of a system used for the ultrasonic imaging apparatus of the present embodiment. That is, in the ultrasonic imaging apparatus of this embodiment, the microcomputer 6 for controlling transmission and reception, the timing generator 8 and the transient memory 10 for the reception signal are connected by the data bus 11, ultrasonic signals to transmit from the array 1 ₀ is given from the driver 12 controlled by the timing generator 8.

The driver 12 includes a transmission amplifier and a modulation circuit including a switch circuit using a power FET (not shown).

Then, using the walsh function, each transmitter 1 _m (m = 1 to 16)
Transmitting signal pulses (not shown) receives a unique modulation strikes the object (not shown) in the same manner, when the reflected wave reaches the receiving array element 4 _0, the received signal, the multiplexer having a A / D converter (not shown) 14 temporarily stores in the transient memory 10 as a series of signals ordered for each of the receivers 4 _n (n = 1 to 8), and the data is transmitted to the microcomputer 6 according to the instructions of the microcomputer 6 and the timing generator 8. It is captured.

The conversion timing pulse of the A / D converter used in the multiplexer 14 is synchronized with a reference clock used for generating a transmission wave. The multiplexer
A / D converters arranged in parallel can be used instead of 14. Since the timing generator 8 is a binary logic signal for both the carrier wave and the modulation wave, the timing generator 8 is constituted by a switch that can be turned on and off alternately, and a rectangular wave is used as the drive signal. Since the signal was a binary signal as a whole, the circuit could have a very simple configuration.

The microcomputer 6 constitutes the arithmetic means of the present invention, and includes a timing generator 8, a transient memory 10, a driver 12, and a multiplexer 14.
This constitutes the transmitting / receiving means of the present invention.

The modulation of the ultrasonic carrier by the above-mentioned walsh function will be described with reference to FIGS. FIG. 3 is a schematic diagram of a modulation circuit based on a walsh function incorporated in the driver 12. The 50 kHz ultrasonic wave output from the carrier oscillator 16 is applied to a phase modulation circuit 18 _m provided for each transmitter 1 _m. It is here After phase-modulated by the modulation wave predetermined for each Sohako 1 _m from the walsh function generator 20 for each Sohako 1 _m, from the output circuit 22 _{m (m} = 1~16) Transmitter 1 _m
Output to

Figure 4 is the a carrier and the signal wave for modulation, which is input to the phase modulation circuit 18 _m, a diagram exemplarily shows a modulated transmit waveform. That is, in this example, when a pulse wave having a sine curve waveform of eight carrier waves as one output unit is phase-modulated by a walsh function waveform formed by changing the phase indicated by a to c by 180 °, for example, The transmission pulse waveform shown in FIG. Since the modulation needs to be synchronized between the transmission system and the reception system, a signal obtained by dividing a carrier wave was used as a clock signal for generating a Walsh function. Generate 16 types of modulated waves modulated by the above, each transmitter 1 _m
Are transmitted at the same time.

As described above, the signals are transmitted from the 16 transmitters 1 _m and 8
Data taken from pieces of受波Ko 4 _n to the microcomputer 6, the reflected signal input as time-series data for each受波Ko 4 _n is correlation detection with each transmission waveform. Then, correlation data including information on the reception time and intensity of the waveform transmitted from the same transmitter 1 _m and received by each receiver 4 _n is stored. This is performed for all received signals for one transmission.

The data for each receiver 4 _n obtained by the data processing,
The data transmitted from the same transmitter 1 _m can be arranged by the parameters of the same walsh function. In this way, the received signals transmitted from each transmitter 1 _m and reflected by the same target object can be grouped.

Next, referring to FIGS. 5 and 6, an outline of a process of detecting an underwater object by a reflected wave and specifying its position on coordinates will be described. Actual transmit signal is propagated as a spherical wave centered on the Sohako 1 ₁ is a sound source, figure describes only the signal wave transmitting from a particular Sohako 1 _1, to simplify the drawing understanding Made it easier. The plane shown in the figure is not a plane, but is a developed view of a conical surface connecting the object and the receiver 4 _n (only four are shown). And Figure was to represent the position of the wave that moves from moment to moment with the lapse of time from the start time t _0.

These figures are transmission pulse 24 from a particular Sohako 1 ₁ propagates water strikes the object 26, resulting reflected pulse 28 has reached the受波Ko array 4 ₀ propagates through the water, receiving circuit 30 _The pulse signal 32 _n propagating in _n (FIG. 1) is taken into the microcomputer 6 together with the time difference data arrived as data according to the above-mentioned processing procedure, and is subjected to the data processing.

The transmission pulse signal is the transmission pulse 24 shown in FIG.
In addition to the above, there are transmission pulses from the other 15 transmitters 1 _m , which are actually much more complicated than in FIG. That is, the pulse signal 32 _n propagating in the receiving circuit 30 _n shown in FIG. 5 is not only one pulse for one transmission but also one object 26 _n.
It is input to the receiving circuit 30 _n is also one after another 16 reflected wave signal with respect.

Next, the data processed by the microcomputer 6 is supplied to a mini-computer 34, where the outline of the means for calculating the image of the target object from the received signal will be described with reference to FIG. That the time when the reflected wave reaches受波Ko from the same object, it is possible to simulate a three-dimensional shape to the traveling direction of the pulse waveform when the reflected wave passes through the receiving array element 4 _0. The minicomputer 34 constitutes means for calculating an image of a target object from the received signal of the present invention.

Therefore, when the reflected wave reproduced as data is reversed, the reflected wave converges to the reflected position, so that the intensity of the reflected wave at each position in the space can be obtained. That is, the reflection position of the object and the intensity of the reflected wave at that position are obtained from the reception time delay of each receiver, and the calculation is performed for each transmitter 1m, so that the space of the sound field intensity due to the reflected wave by the object 26 is calculated. Distribution data can be obtained with high accuracy.

That is, although the conventional image forming performance largely depends on the performance of the transmitting / receiving array, the apparatus of this embodiment can improve the computer performance and improve the software even if the same transmitting / receiving array is used. It is possible to improve the detection performance by developing.

The data can be displayed on the screen of the display device 36 as a three-dimensional image by, for example, displaying a distant object (that is, an object that takes a long time to converge) dark and a close object brightly. By performing the above operation for each transmission, the object can be displayed on the display device 36 as if the object were directly viewed. Of course, it can be simply stored as data or displayed by a printer.

Compare the performance of the ultrasonic imaging device with the following specifications with the conventional device that scans the search area with an ultrasonic beam using a cross array that is arranged vertically and horizontally using a linear transmission array with a conventional directional transmitter. It is described below.

As described above, the device of the present embodiment showed much higher performance than the conventional device. In particular, it is understood that the shortening of the image reproduction time and the increase of the viewing distance make it possible to give the acoustic holographic sonar a very high practicality.

〔The invention's effect〕

As described above, the ultrasonic imaging apparatus of the present invention two-dimensionally arranges a plurality of omnidirectional ultrasonic transmitters and receivers on a plane intersecting the transmission direction and the receiver direction. A quadrature function that generates a group of pulse waves that are orthogonal to each other by distributing transmitting / receiving arrays and providing orthogonal function groups obtained by changing the parameters of the orthogonal function formula consisting of Walsh functions for each transmitter. Generating means, a modulating means for phase-modulating a transmitting carrier by a modulating pulse wave for each of the transmitters, and an ultrasonic pulse transmission signal provided from the modulating means is simultaneously transmitted from the transmitter, Means for simultaneously receiving the reflected wave of the transmitted pulse signal from the object by the plurality of receivers, obtaining the received signal, and transmitting / receiving the ultrasonic signal which repeats the transmission / reception similarly. When,
The signal received for each receiver is subjected to correlation detection using the transmission signal of each transmitter, separated into signals for each receiver, and the received signal delay time and signal for each receiver are separated. Calculating a reflection position from the intensity and a reflection intensity at the position, and calculating a spatial distribution of a sound field reflected from the entire received signal; and a spatial distribution of the sound field intensity obtained by the calculation means as an image. Since the configuration including the image processing means for displaying on the display device is provided, the following effects can be obtained.

That is, (1) the apparatus of the present invention does not require a scanning means for converging a transmission signal to a target position, so that data can be collected at a high speed, an electronic circuit is simpler than a conventional one, and characteristics of individual transmission and reception elements are different. And the degree of dependence on the mounting accuracy can be reduced.

(2) Even if the number of transmitting / receiving elements is reduced, a clearer image can be obtained in a wide visual field range than before. At that time, the computer having an appropriate calibration means can correct the characteristics without using an amplifier.

(3) Since the transmitting / receiving array can be reduced in size,
The degree of freedom in arranging the transmitting and receiving arrays can be increased depending on the equipment to be mounted, such as a ship or an underwater probe.

(4) Even if the same transmitting / receiving array is used, software,
The performance can be improved in accordance with the development of computer technology. (5) By using a computer, high-speed processing is possible and the image reproduction calculation time can be shortened.

[Brief description of the drawings]

FIG. 1 is a front view of a transmitting / receiving array used in the ultrasonic imaging apparatus of the embodiment, FIG. 2 is a block diagram for explaining an outline of a control circuit used in the embodiment, and FIG. 3 is used in the embodiment. FIG. 4 is a block diagram illustrating an example of a modulated transmission signal waveform, FIG. 5 is a diagram illustrating transmission and reception of the apparatus of the embodiment, and FIG. The figure is an explanatory diagram of means for obtaining the position and shape of the object from the obtained data. 1 _m …… Transmitter, 4 _n …… Receiver, 5 …… Transmitter / receiver array,
6 ... microcomputer, 8 ... timing generator, 10 ... transient memory, 12 ... driver, 14 ... multiplexer, 34 ... minicomputer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumasa Okuma 5-27-7-201, Midoka, Midori-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Hajime Yuasa 1427 Yanoguchi, Inagi-shi, Tokyo (72) Invention Norio Ishii 3-2-23-111 Fujimi-cho, Higashimurayama-shi, Tokyo (56) References JP-A-63-106585 (JP, A)

Claims (1)

(57) [Claims] 1. A transmitting / receiving array in which a plurality of omnidirectional ultrasonic transmitters and receivers are two-dimensionally dispersedly arranged on a plane intersecting a transmitting direction and a receiving direction. Provided, corresponding to the orthogonal function group obtained by changing the parameters of the orthogonal function formula consisting of Walsh functions for each transmitter,
Orthogonal function generating means for generating a group of pulse waves orthogonal to each other, modulating means for phase modulating a transmitting carrier wave by a modulating pulse wave for each of the transmitters, and an ultrasonic pulse transmitting means provided from the modulating means. A signal is simultaneously transmitted from the transmitter, and a reflected wave of the transmitted pulse signal from the object is simultaneously received by the plurality of receivers, and the received signal is obtained. The ultrasonic wave transmitting and receiving means which repeats the above, and the signal received for each receiver is subjected to correlation detection using the transmitted signal of each transmitter, separated into signals for each receiver, and separated. Calculating means for obtaining a reflection position and a reflection intensity at the position from the reception time delay of each receiver and the signal intensity with respect to the signal, and obtaining a spatial distribution of a sound field reflected from all the reception signals; Distribution of the sound field intensity obtained by means Ultrasound imaging apparatus having an image processing means for displaying on the image display device.