JPS59131338A - Method and system for forming ultrasonic image - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION In a transducer device comprising a fixed array of adjacent transducer elements, a plurality of groups of transducer elements each comprising adjacent transducer elements are sequentially and periodically selected to generate a transducer. In response to pulsed electrical transmitter signals applied to the element, an ultrasonic beam is created and transmitted into a foreign object substantially in the scan plane and echoes reflected from discontinuities in the object are generated. the transmitter signal and/or the transmitter signal being adapted to generate an electrical echo signal in response to the receiving element and applying the transmitter signal to a transducer element in a selected group of transducer elements;
The echo signals provided by the transducer elements are such that signals for transducer elements located far from the center of the group of transducer elements have a hue lead relative to signals for transducer elements located in the center. The present invention relates to a method for creating cross-sectional images in which transducer elements are time-shifted relative to each other as a function of their distance from the center.

The invention also relates to an ultrasound imaging system for implementing such a method.

Conventionally, a method of mechanically moving an ultrasound transducer has been used to form an ultrasound image (more specifically, a cross-sectional image). This has some drawbacks. - That is, if the transducer were to be moved by hand, the scanning process would be very long and dependent on the skill of the operator.

If the transducer is motorized, a relatively heavy aquarium is usually required. Furthermore, the extra travel distance in the aquarium results in a reduction in the maximum possible image field wave.

To eliminate these drawbacks, ultrasound imaging systems that incorporate electronic scanning have been developed. In this method the ultrasound beam is shifted linearly in time.

In a known ultrasound imaging system as described above (U.S. Pat. No. 3,881,466), a transducer device creates an unfocused ultrasound beam, and the lateral resolution is determined by the width of the transducer element. . In this known system, there is a limit to the lateral resolution that can be improved by decreasing the width of the transducer elements, set by the minimum width of the ultrasound beam. Although the cross-sectional images obtained with this known system are relatively congested, there are still many applications where higher lateral resolution is desired in practice.

A method of the kind to which the invention mentioned at the outset relates is described in US Pat. No. 6,919. A disadvantage of the method disclosed in the '683 patent is that the beam width cannot be substantially narrowed over the entire sample depth. This method is therefore unsatisfactory for many applications (particularly medical diagnostics) where a significant reduction in beam width and thus an increase in lateral resolution over the entire sample depth is desired. However, such a It is known that amplitude weighting increases the width of the main beam of the ultrasound field in the far field region. 1968
July issue of Ultrasonics 153-15
T, C on page 9.

“Electronic Fan Scanning for Medical Diagnosis” by Somer.
E1eCtrO! 111c 5eCtOr Sca
nnning for u'ultrasonicdiag
see ) J.

A known method for obtaining high lateral resolution across the whole subject is so-called dynamic focusing, which is implemented using an array of transducer elements (U.S. Pat. No. 3,090,030). reference).

This type of focusing involves providing a delay that is variable over time between the transmitter signals applied to the transducer elements (so that the location of the focus varies over time along the main axis of the beam across the test object). can be changed.

An important drawback of this known method is that it requires relatively complex and therefore expensive electronic circuitry.

It is therefore an object of the present invention to provide a method and system capable of providing a relatively high and advantageous lateral resolution over the entire subject for medical diagnostic purposes with a minimum of equipment. be.

The method according to the invention comprises: (a) focusing the transmitted ultrasound beam and/or the corresponding reception characteristics to a focal line in the scanning plane by means of a time shift imparted to the transmitter signal and/or the echo signal; (b) (C) focusing the transmitted ultrasound beam and/or corresponding receiving characteristics to said focal line also in a plane perpendicular to the scanning plane; and (C) adjusting the amplitude of each transmitter signal and/or echo signal to A weighting factor determined as a function of the distance between the transducer elements and the center of the group, which is greater for signals for inner transducer elements in the group than for signals for outer transducer elements. It is a weighting coefficient, and is characterized by including giving weighting.

The present invention also includes a timing generator for generating a pulsed electrical timing signal and an identified array of adjacent transducer elements responsive to a pulsed transmitter signal derived from the timing signal. a transducer device for transmitting an ultrasound beam substantially in a scanning plane into a foreign object, receiving reflected echoes from discontinuities in the force-searched object, and producing an electrical echo signal in response thereto; A timing generator and a plurality of transducer element groups connected to the transducer device and the display device and configured of adjacent transducer elements in Moehi transducer device #:a are firstly periodically selected to generate the transmitter signal. a transducer element selection device for applying the echo signals produced by the transducer elements to the transducer elements in the selected group of transducer elements to the display device for conversion into a visible image representative of the cross-sectional structure of the foreign object; interposed between the generator and the transducer element selection device, the transmitter signals being time-shifted relative to each other for the transducer elements in the selected group of transducer elements are extracted from the timing signals generated by the timing generator; - a transmitter signal generating transmitter device inserted between the transducer element selection device and the display device;
(an echo signal receiver device that creates a relative time shift between said echo signals created by a time-shifted transmitter signal and/or
The temporal position of the echo signal is such that the signal for a transducer element far from the center of the selected transducer element group has a phase lead with respect to the signal for a transducer element in the center. The present invention relates to a cross-sectional imaging system in which t is determined as a function of the distance between the center of the element group, and its characteristics are as follows: (a) the above time shift is caused by the transmission ultrasonic beam and/or reception characteristics being scanned; It is chosen so that it is focused to a focal line in the plane,
)) The shape of the transducer device or the structure of the transducer device in combination with the time-shifted transmitter signal and/or the echo signal may cause the transmitted ultrasound beam and/or the corresponding receive characteristics to be aligned in a plane perpendicular to the scanning plane. (C) the transmitter device and/or the receiver device are adapted to focus the transmitter signal and/or echo signal on the focal line at the center of the transducer element and the group of transducer elements; a weighting factor determined as a function of the distance between the transducer elements, with greater weighting for signals on the inner transducer elements 1 in the group of transducer elements than on signals for the outer transducer elements. It includes means for weighting with coefficients.

The technical effect achieved by the method and system according to the invention is that ultrasound images with a relatively high and advantageous lateral resolution for medical diagnostic purposes can be obtained with a minimum of equipment (and therefore at a relatively low cost). ) Moreover, it is possible to obtain the entire examination depth.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings.

The transducer apparatus 11 of the known ultrasound imaging system (U.S. Pat. No. 3,881,466) shown in FIG. 1 includes an elongated fixed array of adjacent transducer elements 12. adjacent elements 12
The 0 groups are sequentially excited to generate pulses. The position of each successive group of A elements is shifted from the position of the immediately preceding group by a vertical distance of B The A elements in the transducer group move in the direction of the arrows, as shown by a series of dot-dashed rectangles 14 indicating the position of the beam 13 at each time interval. The known transducer device 11 shown here uses an unfocused ultrasound beam 1, since all are excited at the same time.
It should be noted that 3. The unfocused radiation characteristic 22 of the ultrasound beam of FIG. 1 is shown in the second diagram.

In FIG. 1, a Cartesian coordinate system is defined by three arrows Q, , L, 'S. Principal axis direction of sound wave beam 13: (parallel).

Arrow Q is a flat x K N angle defined by arrow mark and S. The position of the cross-sectional view and the front Z shown in the attached drawings are determined by this coordinate system;
A preferable configuration of the 7th straight line 38 is shown diagrammatically, including the knee surface. The structure 38 includes a complete electrode 36 that is grounded and one surface 37 that is used as a radiating surface.
Contains. Structure 38 also includes piezoelectric layer 35 and electrode segment l-3 as shown in the back view of FIG.
1-34 included.

From the above description of the arrangement 38, it is clear that the transducer elements according to the invention 1 can have common parts, such as the piezoelectric layer 35 and the complete electrode 36. The arrangement 38 according to the invention It can be actuated by simply providing an electrode segment on one side, feeding it with a time-shifted transmitter signal and obtaining an echo signal therefrom.In this way, each electrode segment Define the element.

The advantages achieved by the present invention, namely the high lateral resolution, are primarily due to the new mode of operation of the transducer device.
This will be explained in detail with reference to No. 57.

FIG. 4 shows the electrode segments 31-34 of the transducer group 21 according to the invention, transmitter signals time-shifted relative to each other as shown in FIG. 5 to generate an ultrasound beam according to the invention. 41.4
2 is applied to electrode segments 31-34. The transmitter signals for the outer segments 31.degree. 34 have a phase lead. In this way, a loosely focused ultrasound beam 23 is created (FIG. 2).

In a preferred embodiment of the invention, time shifts are created not only between the transmitter signals but also between the echo signals received by the individual elements of the transducer group.

The transducer group 21 shown in FIG. 4 has four elements for transmitting and receiving, and the transmitted signal and the time-shifted echo signal of the outer elements have a phase lead of 90°. have. According to the invention, the phase lead is determined by the period (360°) of the high frequency carrier signal (e.g. 2'11Jz).
). The carrier signal is applied to the electrode segments of subsequent groups in the form of pulses, for example with a recall frequency of '1 KHz, and at a suitable phase angle.

The effects of the transducer details 21 according to the present invention are as follows (
1) It can be improved by -f3j.

(1) It has been found advantageous to choose the combination of phase leads for the outer elements of the group as approximately 90° for the transmitter signal and 45° for the echo signal or approximately 45° for the transmitter signal and 90° for the echo signal. As a result of using these different values of phase advance for the transmitter and echo signals, the radiation profile according to the invention (FIG. 2) can be additionally narrowed over a certain depth.

(2) It is advantageous to weight the transmitter and echo signals. As shown in FIG. 5, the inner electrode segments 32, 33 are supplied with a transmitter signal with a larger amplitude aO. Similarly, echo signals received from inner segments are multiplied with a larger weighting factor than echo signals from outer elements.

Preferably, the weighting ratio for both the transmitter signal and the echo signal is 2:1.

(3) Also in the Q direction shown in FIG. 1, for example, a transducer arrangement (
It is advantageous to create a loose focusing by using a 200° C. (see No. 6). Loose focusing in the Q direction can also be created electrically using a transducer arrangement, such as that shown in FIG. 7, in which each electrode segment is divided into six parts a, b, c in the Q direction. As shown in FIG. 7, only the shaded portion of this segment is used for transmission and reception. Inner portion 32b.

331) is stimulated by the transmitter signal 41, and the rest.

The active part of is excited by a transmitter signal 42.

In such a system, a transducer arrangement with a flat radiating surface may be used, resulting in an electrically more resilient configuration than would be the case with a transducer arrangement having a curved radiating surface, and would be less expensive.

In the known transducer device 11 shown in FIG. 1, the ultrasound beam 13 can be moved by a transducer element 120 width after each transmission and reception period. However, if the ultrasound beam could be moved a smaller distance at each point in time, for example by half the length of the element, the number of 1,000 lines would increase and the resolution would increase. Of course, the same effect could be obtained by halving the width of the elements, but then the number of elements would be doubled and thus the complexity would increase.

Preferred embodiments of the invention (Figures 8a, 8b, 8c)
In Figure), the ultrasound beam is moved by half the width of the element. The successively selected groups 71, 72, 73 of transducers then alternately contain odd and even elements. Subsequent groups are formed alternately by decreasing the number of segments in one direction and increasing them in the opposite direction. The amplitude and phase of the transmitter signal or time-shifted echo signal are chosen such that the shape of the ultrasound beam remains substantially uniform, independent of the number of elements in the transducer group. For example, the relationship between the shooting angle and the phase shown in Table 1 and Table ■ is 4 elements and 3 elements alternately! (
When used, 1 gives a very similar beam shape.

Table I (For 4 elements) Table ■ (For 3 elements) The embodiments described above in connection with Figures 1 to 8 are ideal when the ultrasonic waves are strongly focused. It can be called spherical focusing because it focuses in the form of a strip that becomes a single point (focal point).However, according to the description related to Figures 2 and 6, only loose focusing occurs. , the ultrasound beam will actually have a narrow width rather than a focal point. A different type of focusing is carried out, i.e. focusing along a line which should be called a focal line rather than a focal point, which is why the latter is called aspheric focusing.

The second embodiment of the present invention will first be described with reference to Figures 9a, 9b and 10. It is known that it can be focused effectively over long distances (Swiss Patent No. 543.313). Wavefronts of this type are emitted, for example, by conical ultrasound transducers.

In accordance with the present invention, if the phase angle ψ can be made to increase linearly with the distance between the transducer elements 92-98 and the center of the transducer group, the transmitter signals 101-104 shown in FIG. In the case of the time-shifted echo signals 202-208 of FIG. 16, a conical radiation surface can be approximated. FIG. 10 shows the linear increase in phase angle ψ. By shaping the emitting surface 37 in the Q-direction as shown in cross-section in FIG. 9b, a linear increase in the phase angle of the reflected ultrasound waves can be achieved. The dotted line 107 in FIG. 9a indicates the position of constant phase on the emitting surface of the transducer device. Because of the t@leather, instead of a phase that changes stepwise as in this example, this drawing shows a phase that changes continuously in the L direction. In this example, the constant phase slash is a set of straight lines 107 rather than circles as in the case of a conical wavefront.

A better conical wavefront approximation is obtained by means of an inventive embodiment shown below first in FIGS. The phase angle of the reflected echo signal is a quadratic function of the position of the corresponding element in the center of the transducer group and a linear function at the ends.The corresponding phase angle distribution in the Q15 direction is This is obtained by shaping the cross-section of the device as shown in FIG. 11b. The line 37 in FIG. 11b is preferably a hyperbola. Such curves
At °7 it is a circle and at the ends it is a straight line. The improvement obtained in this example is that the constant phase trajectory 10 shown in FIG.
This is illustrated by the fact that 6 now has rounded corners.

It should be noted that the radiation group of the transducer in the embodiments shown in FIGS. 9a and 11a has a wider area than in the embodiment shown in FIG. be. This large area allows for the larger aperture needed to obtain higher resolution.

In the embodiment Kb described above, as in the previously described embodiments, the inner part of the radiating group of the transducer has a larger mold width, so that the echo signals received there are given a greater weighting upon reception. Combined with the coefficient, it is possible to improve the short range field.

Group 21 and elements 31-34 as shown in FIG. 4 to obtain a loosely focused ultrasound beam 23 as shown in FIG.
The shape of will be first explained with reference to FIGS. 18 and 19. The transducer group provides effective loose focusing when its width W and length t are 15 to 30 times the wavelength. The radius of curvature R (FIG. 19) of the wavefront is made equal to half the depth of the object to be examined, preferably somewhat smaller. In the case of a transducer group containing 4 elements, the width of the individual elements is such that the phase between the waves emitted from adjacent elements is not much greater than 90°. If the values of these radii of curvature and phase difference exceed the above-mentioned values, corresponding disturbances in the shape of the beam appear and the lateral resolution is therefore also degraded. However, uninvention: loose focusing follows:
Well, at least in principle j can be obtained with a phase difference between 30° and 180°.

Next, the shape of the transducer element will be explained with reference to specific examples (FIGS. 18 and 19). As shown in Figure 18, the inner two elements of the group transmit with a phase of O0, and the outer two elements transmit with a phase of 90°. From Figure 19 and the string theorem, the following equation is obtained. (1) is obtained.

d,2=2R·Δ (1) where dl is the tangential shift to obtain the desired 90′ phase shift, R is the radius of curvature of the wavefront and the distance corresponding to the 90° phase shift. In this case, if the wavelength is λ, the equation (2) is obtained.

λ 4 ′ (2) If R is 80ffllll! (approximately half the depth of the object to be inspected)
and λ is 0.75 mm (this wavelength corresponds to a frequency of 2 MHz), then dl is 5.481111
! becomes. The element is located at a distance e from the center of the transducer group.
Assume that it is 1 at L2-43mm. This value of d2 is equal to the previously calculated distance d1.

FIG. 13 is a block diagram of an ultrasound imaging system according to the present invention, using a seven element transducer group for transmitting and receiving, as shown in FIG. 11a. The block circuit diagram of FIG. 13 is similar to that of FIG.
33, transmitter signal generation 5133 to line 13
5 to the element selector drive switch 138, a timing generator 131
an element counter and decoder 136 for controlling a switch 138 connected to an echo message 142 sent from the transducer group, an echo signal receiver 14;
3. Combined echo signal 144 at the output of echo signal receiver 143, time-sensing amplifier 145, detector 1
46, signal output 147, output signal 148 of output 147, X deflection generator 151, X deflection generator 151
A deflection signal 154 is provided by a Y-stage function generator 152, an inter-stage number signal 155 is sent out from a Y-stage number generator 152, and a Tsushiro code 156 is shown having six inputs, X, Y, and Z.

Timing generator 131 generates periodic timing pulse 1
32 to trigger the transmission of the ultrasound signal and generate the necessary sinusoidal signal. The transmitter signal generator 133 generates four electrical transmitter pulses 121-124 (
(see FIG. 14) is generated. 6 signals 122, 12
3.124 is + for signal 121 with a phase of 0°
It has phase leads corresponding to carrier signal phases of 60°, +100°, and +180°. These transmitter signals are sent out on line 134. In the element selector drive switch 138, transmitter signals are applied to seven supply lines. The transmitter signals on the other lines are +180°, +100°, +30°,
It has phases of 0°, +30°, +100°, and +180°. Element counter and decoder 136: Drives the desired seven elements for transmission or reception through switch 138. After each pulse, the shape in Figure 11 is shifted by one element in the L direction. Similarly, the transmitter signal is periodically interchanged with another phase on the supply line so that each element obtains a corresponding transmitter signal with the correct phase.Echo signal 14
2 reaches the echo signal receiver 143 from the seven switched-on elements. The signals are then given different delays, multiplied with different weighting factors, and summed. The output signal 144 of the receiver 143 passes through a time-sensing amplifier 145 that compensates for attenuation in the tissue being examined. The signal is then rectified by a detector 146 and passed through a processor 147 to an Oscilloscope coder 156.
An error occurs when input to the z input. The processor 147 is the detector 14
compresses the dynamic range of the signal sent out from 6.

The X-deflection generator 151 generates a voltage proportional to the elapsed time since the last pulse was sent.

Y stage function generator 152 generates a voltage proportional to the central axis position of the switched-on group of transducers.

Configuration and operation of transmitter signal generator 133.

will be explained with reference to FIGS. 14 and 15. The timing pulse 132 triggers the pulsed high frequency generator 161 and outputs the output signal 16 of the generator 161.
2 (pulsed carrier signal) has phases O0, 30°, 100°
, 180° in a tap delay line 163 to obtain four signals with 180°. These signals are multiplied with corresponding weighting factors in weighting devices 164-167.

FIG. 16 shows the echo signal receiver in detail. Echo signals 142 are multiplied with corresponding weighting factors in weighting devices 171-177.

They are delayed by phase shifters 181-185 and summed in adder 186.

Element selector drive switch 13 in the system of FIG.
The basic principle of the preferred embodiment of No. 8 will first be explained with reference to FIG. Although the apparatus of FIG. 16 uses a group of seven elements, for the sake of simplicity, the principle will be described here for a transducer group containing four elements. The switching diaphragm shown in FIG. 17 can be used to perform tri-shifting of a group of four transducer elements. The inner two elements of each group (e.g. elements 32 and 33 of group 1) transmit the transmitter signal 41 as shown in FIG.
The two outer elements (e.g. elements 31 and 34 in one group) receive the transmitter signal 42 as shown in FIG.
The bird is given a try. In FIG. 17, the transducer elements are shown with corresponding electrode segments 31, 32, 33, etc.

By means of switch means 191, the transducer elements are periodically connected to the 4' supply lines 192-195. These four lines are connected through switch means 196 to two supply lines 197 and 198. This 2
The main lines 197 and 198 are supplied with transmitter signals 41 and 42 having amplitudes and phases similar to the fifth threshold. Figure 17 shows two successive transuser groups 1
(11), shows the switch position for ■ (dotted line).

The device f- for controlling the switch means 191 is not explained. In the switch means 196 (well, in order to drive a new group, each switch (e.g. 213) is connected to an upper switch (e.g. 21) to drive the previous one group.
2) is placed in the same position previously occupied. Top: (One switch 211 is placed in the position previously occupied by the bottom switch 214. If the electronic design of the switching means is suitable, the same switch can be used for transmitting and receiving.

If it is necessary to use separate electronic switches for transmission and reception, another circuit similar to the one shown in FIG. 17 may be prepared using separate supply lines for transmission and reception.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a transducer device of the conventional ultrasound imaging system previously described. FIG. 2 shows a cross section of the radiation profile of the transducer group compared to the loosely focused radiation profile of the transducer group in the device of FIG. 6 is a cross-sectional view of a preferred embodiment of the transducer arrangement of the transducer apparatus of FIG. 1; FIG. FIG. 4 shows a back view of the transducer group of the arrangement shown in FIG. 3 for four transducer elements. FIG. 5 shows the waveform of the transmitter signal applied to the electrode segments of the transducer group of FIG. 3. FIG. 6 includes the group with the first element of the emitting surface in the arrangement of FIG. 3, but for the sake of simplicity FIG.
The principle is illustrated for the case of a transducer group containing only 2 elements. Figures 18 and 19 show the shape of the transducer group and its elements. Agent Akira AsamuraFig, 6 Fig, 7 1 LL L
LLFig, IO Fig, 12 Fig, 14 1 house 3 Fig, 15

Claims (9)

[Claims] (1) A pulsed electrical transmitter that sequentially and periodically selects a plurality of transducer element groups composed of adjacent transducer elements in a transducer device composed of a fixed array of adjacent transducer elements and applies pulsed electrical signals to the transducer elements. In response to the signal, an ultrasonic wave is created and transmitted into the foreign object substantially within the scan plane, and the echoes reflected from the discontinuities in the object are received and responded to. said transmitter signal applied to a transducer element in a selected group of transducer elements and/or said echo signal provided by a transducer element includes said transmitter signal applied to a transducer element in a selected group of transducer elements to generate an electrical echo signal; as a function of the distance between the transducer elements and the center of the group of transducer elements in such a way that the signals for transducer elements that are far away from the center of the group have a phase lead with respect to the signals for transducer elements that are in the center. A cross-sectional image creation method that can give time shifts to each other,
a) The ultrasound beam transmitted by the above time shift and (
or) focusing the corresponding receiving characteristics into a focal line in the scanning plane; (b) the transmitted ultrasound beam and/or
(C) the amplitude of each transmitter signal and/or echo signal is dependent on the amplitude between the transducer element and the center of the group of transducer elements; A weighting factor determined by a function of distance for signals for inner transducer elements in a group of transducer elements than for signals for outer transducer elements; A method characterized in that it includes giving. (2) a timing generator for generating a pulsed electrical timing signal; and a fixed array of adjacent transducer elements for generating ultrasonic waves in response to a pulsed transmitter signal derived from the timing signal. a transducer apparatus for transmitting a beam substantially in a scan plane into a foreign object and for receiving reflected echoes from discontinuities in the object and producing an electrical echo signal in response; A plurality of transducer element groups connected to the transducer device and the display device and constituted by adjacent transducer elements in the transducer device a transducer element selection device for converting the echo signals applied to the transducer elements and produced by the transducer elements into a visible image representative of the cross-sectional structure of the foreign object, the timing generator and the transducer element selection device; a transmitter signal generating transmitter device interposed between the device and the device for deriving mutually time-shifted transmitter signals for transducer elements in a selected group of transducer elements from the timing signal generated by the timing generator; an echo signal receiver device interposed between the transducer element selection device and the display device to create a relative time shift between the echo signals produced by the transducer elements; The temporal position of the signal and/or echo signal is such that the signal for a transducer element located at a greater distance from the center of the selected group of transducer elements has a phase lead with respect to the signal for a transducer element located at the center. 1. A cross-sectional imaging system, wherein the shape is determined as a function of the distance between the transducer element and the center of the group of transducer elements,
The above time shift is the transmitted ultrasound beam and/or
(b) the shape of the transducer device or the shape of the transducer device in combination with a time-shifted transmitter signal and/or an echo signal; (C) said transmitter device and/or said The receiver device transmits the transmitter signal and/or the echo signal to an inner transducer in the group of transducer elements with a weighting factor determined by a function of 1 of the distance between the transducer element and the center of the group of transducer elements. element; a system characterized in that it includes means for weighting the two signals with a weighting factor that is greater than the signal for the outer transducer element. (3) Claim 2 (wherein the phase angle of the time-shifted transmitter signal 8 and/or echo signal is linear in proportion to the distance of the transducer element from the center of the group of transducer elements) A system characterized by a stepwise increase in (4) In claim 2, the phase angle of the time-shifted transmitter signal and/or echo signal is expressed by a hyperbolic function as the distance between the transducer element and the center of the group of transducer elements increases. A system characterized by a stepwise increase in (5) In claim 2, the phase angle of the time-shifted transmitter signal and/or echo signal increases stepwise with the distance between the transducer element and the center of the transducer element group, A system characterized in that the increase is quadratic near the center of the transducer elements and linear at the ends. (6) Claim 2 provides that the radiation surface of the transducer device has q in cross section.
This system is characterized by a T-shaped line. (7) The system of claim 6, wherein the V-shaped line is made up of two straight line segments. (8) The system according to claim 6, wherein the V-shaped line is hyperbolic. (9) Claim 2, paragraph 1 (wherein, the transducer element is segmented into an upper part, a middle part, and a lower part along the longitudinal axis of the element, and the upper part of the outer element in the transducer element group The lower part is used for neither transmitting nor receiving, and the transmitter signals for the upper and lower parts of the inner element have at least a smaller amplitude or are phase shifted compared to the transmitter signals for the central part! qO) In claim 2, the time shift between transmitter signals and/or the time shift between echo signals for adjacent transducer elements is determined by the phase of the radio frequency carrier included in each transmitter signal or echo signal. 1. A system, characterized in that the absolute value of the phase shift is in the range between 30° and 180°.