JPS61114118A - Exciting and driving method of transducer - Google Patents

Abstract

PURPOSE:To widen the band of an ultrasonic wave easily with high precision by setting the pulse width of at least one of burst waves consisting of a pulse group for exciting and driving applied to the piezoelectric element of a transducer different from others. CONSTITUTION:A pulse transmitting circuit 6 transmits a burst signal S1 consisting of a pulse group responding to the control signal of a circuit 14. The pulse width of this wave S1 is set different with time; t1>Tp>t2,t3=t4= Tp, and t5<Tp (Tp: the half period of the natural frequency of an ultrasonic wave determined by shape and thickness of the piezoelectric element), where t1-t5 are the pulse width varying from the beginning of the transmission successively. The width t1 is made longer than oscillation Tp to oscillate the piezoelectric element and give inertia, the width t2 is shortened to increase the frequency and excite and drive oscillation with the same widths t3 and t4 with the oscillation Tp, and the width t5 is shortened to provide dumping effect. Consequently, the frequency component of the ultrasonic wave is widened in band to reduce trailing of the ultrasonic wave. Thus, excellent picture quality is obtained from the shallow part to the deep part of an object.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates primarily to a method for excitation driving a transducer used in an ultrasonic diagnostic apparatus.

(b) Prior art and its problems Conventionally, there are two methods of excitation driving a transducer used in ultrasonic diagnostic equipment: impulse excitation with a steep voltage change as shown in Fig. 3, and the method shown in Fig. 4. There is also one based on burst wave excitation consisting of a group of pulses as shown. In burst wave excitation, the frequency components of the ultrasonic waves emitted from the transducer are made relatively broadband, but in order to emit ultrasonic waves with the required energy, it is necessary to
Since excitation at a high voltage of about 200 μm is required, the piezoelectric element and the excitation circuit are required to have high dielectric strength. However, recently, electronic circuits are often used for multiplexers, excitation circuits, etc. that selectively switch the piezoelectric elements of transducers, and therefore, there is a problem that dielectric breakdown and performance deterioration occur when high voltage is applied to the excitation circuits. For this reason, a method using burst wave excitation is widely applied instead of impulse excitation. This method allows the transducer to be excited and driven with a relatively low excitation voltage of about 30 to 50 V, so it has the advantage of reducing failures in the electronic circuit, but in the past, the pulse width to of the burst wave was always set constant. Since the transducer is driven by excitation, there is a problem in that the frequency component band of the ultrasonic waves emitted from the transducer is narrow. Zunaichi: The absorption and attenuation characteristics of ultrasonic waves emitted to a subject depend on their frequency components, and although the resolution improves with high-frequency components, the absorption and attenuation by the subject has a large effect, so it is difficult to You can only get information about. Furthermore, even if deep information is obtained from low frequency components, the resolution is lower and the image quality is degraded. Therefore, it has been desired to widen the band of ultrasonic waves by burst wave excitation.

In order to widen the bandwidth of ultrasound, attempts have been made from a structural standpoint, such as adding multiple matching layers to the piezoelectric element and devising the shape of the piezoelectric element, but these techniques require special processing. Therefore, there are inconveniences such as adding time to manufacturing or increasing costs.

(C) Objective The object of the present invention is to solve these conventional problems and to easily realize broadband ultrasonic waves with high efficiency by burst wave excitation.

(D) Structure In order to achieve the above-mentioned object, the present invention provides a burst wave consisting of a group of pulses for excitation driving applied to a piezoelectric element of a transducer, in which at least 61 pulse widths of the pulse group are changed to other pulse widths. I'm trying to set it up differently.

(e) Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus for applying the method of the present invention. In the figure, reference numeral 1 denotes an ultrasonic diagnostic device, and 2 denotes a transducer for transmitting and receiving ultrasonic waves, which includes a plurality of piezoelectric elements (not shown). 4 is a multiplexer for selectively switching the piezoelectric element to be excited and driven in the transducer 2;
8 is a pulse transmitting circuit that transmits a burst wave s+ consisting of a group of pulses for excitation driving as shown in a), and a receiver 8 that amplifies and detects an echo signal output in response to an ultrasonic echo received from the transducer 2. 10 is an image memory circuit that stores the echo signal output from the wave receiving circuit 8 as image data; 12 is an image memory circuit 10;
CRT, 1, which displays image data read from the
Reference numeral 4 denotes a control circuit that controls each of the above sections.

Next, the ultrasonic diagnostic apparatus 1 transmits the transducer 2.
We will explain how to excite and drive.

Applying a control signal from the control circuit 14 to the pulse generating circuit 6,
A burst wave sl consisting of a group of pulses in response to this control signal is transmitted from the pulse transmitting circuit 6. This burst wave sl is set so that its pulse width varies over time, as shown in FIG. 2(a). In other words, now the unique frequency f of the ultrasonic wave is uniquely determined by the shape and thickness of the piezoelectric element.
Let Tp be the half period of
If it2, t3, t4, t5, tl >'rp,
12<Tp, [3=t4=TpXt5<'rp
Set it so that This is because the piezoelectric element is stationary before excitation driving, so initially the pulse width t1 is changed to the natural vibration T
By making the length longer than p, the piezoelectric element is given free vibration and a certain degree of inertia. Next, the pulse width t2 is shortened to increase the frequency, and then the pulse width t3, which is the same as the natural vibration Tp, is
4, the pulse width t5 is shortened in order to provide a damping effect. If you do this, Figure 2 (
As shown in C), the frequency components of the ultrasonic waves are broadened, and as shown in (b) of the figure, the tailing of the ultrasonic waves is also reduced. However, the specific value of the pulse width tl-15 needs to be set to an optimum value in consideration of conditions such as the thickness and constituent material of the piezoelectric element of the transducer 2, and its low frequency characteristics.

When the transducer 2 is excited and driven in this way, the transducer 2 emits ultrasonic waves containing broadband frequency components to the subject, so the transducer 2 receives the echoes of the ultrasound reflected from the subject again. do. Since the transducer 2 outputs an echo signal corresponding to the received ultrasonic echo, this echo signal is sent to the image memory circuit 10 via the multiplexer 4 and the wave receiving circuit 8, where it is stored as image data. .

Then, the image data stored in the image memory circuit 10 is read out by the control circuit I4 and outputted to the CRT. Therefore, the diagnostic image displayed on the CRT has good image quality from the shallow part to the deep part of the subject.

Note that the present invention is not limited to the ultrasonic diagnostic apparatus of this embodiment, but can be widely applied to transducers of ultrasonic equipment. Further, in this embodiment, the burst wave for excitation driving is composed of a group of pulses, but the present invention can also be applied to a case where it is composed of a sine wave.

(f) Effects As described in (2), according to the present invention, since the transducer is excited and driven by a burst wave consisting of a group of pulses, ultrasonic waves having a predetermined energy can be emitted at low voltage. Therefore, an electronic circuit with low withstand voltage can be used. Moreover, since the pulse width of at least one of the pulse groups constituting the burst wave is set to be different from the other pulse widths, even though burst wave excitation is used, ultrasonic waves can be easily and efficiently applied. It is possible to realize a wide band of ultrasonic waves, and also to emit ultrasonic waves with less trailing.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, FIGS. 3 and 4 show a conventional example, and FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus to which the method of the present invention is applied; FIGS. 2 to 4 are explanatory diagrams of a method for exciting and driving a transducer. l ・Ultrasonic diagnostic equipment, 2 transducers, 6...pulse transmission circuit.

Claims (1)

[Claims] (1) A transducer characterized in that, of a burst wave consisting of a group of excitation drive pulses applied to a piezoelectric element of the transducer, the pulse width of at least one of the pulse groups is set to be different from the other pulse widths. Excitation drive method.