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DESCRIPTION JPS60102556

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DESCRIPTION JPS60102556
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic apparatus, and more particularly to a system for extracting an ultrasonic signal with a
good S / N ratio using not only the fundamental resonance mode of an ultrasonic transducer but
also the primary resonance mode. (Background of technology) Looking at the application
example of recent ultrasonic equipment, for example, in the field of geological survey 3 oil
exploration etc., a plurality of receiving probes are provided, and ultrasonic waves received by
each of the probes When a reflected signal is recorded on a medium such as a magnetic tape, the
reflected signal received by each probe is polymerized to improve the S / N ratio. The ultrasound
reflection image in this case is one in which the above recording medium is processed by a
computer and displayed on a display, and focusing on the improvement of the S / N ratio
regardless of the real time property. As another method of polymerizing the above-mentioned
reflected signal and improving the S / N ratio, there is a method of repeating transmission a
plurality of times from one ultrasonic transducer and adding the received ultrasonic signals
together. It has the problem of lack of real time. On the other hand, it has been found that the
ultrasonic transducer has an n-order (generally, n is an odd number) resonance mode in addition
to the fundamental resonance mode. If this characteristic is used, one ultrasonic transducer can
be used. Since ultrasonic waves in a plurality of vibration modes can be transmitted while being
slightly shifted in time, it is expected that the reflection signal can be polymerized to improve the
S / N ratio. The present invention relates to a method of utilizing the resonance characteristics of
a plurality of resonance modes of the ultrasonic transducer. (C1 Prior Art and Problems In the
conventional ultrasonic apparatus, it is necessary to use a wide-band ultrasonic transducer to
simultaneously view, for example, the outline and detailed structure of the subject's internal
organs. However, it is difficult to make a broadband transducer, and even if it were possible,
there was a problem that the efficiency of transmitting and receiving ultrasonic signals was poor,
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and as a result, the S / N ratio was poor. Then, in order to improve the S / N ratio of the
ultrasonic reception wave, a method of superposing the reception waveform is known, but this
method repeats transmission plural times and adds reception reflection waves. Since it takes time
to add up, there is a problem that it is not possible to capture a moving subject in real time. In
addition, there is a method in which ultrasonic waves of a plurality of frequencies are divided and
simultaneously transmitted from the above-mentioned wide band transducer, but each frequency
component of the ultrasonic wave is a single ultrasonic wave due to the problem of withstand
voltage of the transmitting transistor. In comparison with the case of sending out, there is a
drawback such as not being able to obtain a sufficient S / N ratio.
SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an
object of the present invention to provide a method for extracting an ultrasonic signal with a
good S / N ratio without losing real time. (Al Configuration of the Invention and This Object
According to the Invention: (1) The ultrasonic drive circuit drives an ultrasonic transducer to
transmit an ultrasonic pulse to a subject, and an ultrasonic pulse from the subject is detected. An
ultrasonic apparatus for detecting an acoustic wave signal by an ultrasonic transducer includes a
transmission / reception circuit in a fundamental resonance mode and a zeroth resonance mode
of the ultrasonic transducer. (2) A circuit for transmitting ultrasonic pulses in each of the above
resonance modes to the subject with a slight delay, and analyzing the frequency of an ultrasonic
signal from the subject to obtain ultrasonic signals in each of the resonance modes And an
ultrasonic signal synthesis circuit that corrects and adds up time deviations of outputs of
respective resonant modes of the circuit. This is achieved by providing an ultrasonic apparatus,
and has the advantage of being able to extract an ultrasonic signal with a good S / N ratio
without compromising real-time performance. (F) Embodiments of the Invention First, to
summarize the gist of the present invention, in the present invention, an ultrasonic transducer
has an n-order (generally, n is an odd number) resonance mode in addition to a fundamental
resonance mode. The narrow band transducer is intended to extract an ultrasound signal with a
good S / N ratio, focusing on the fact that transmission and reception efficiency is better than
that of a wide band transducer. Specifically, After slightly shifting the time, ultrasonic pulses in a
plurality of vibration modes are transmitted to the subject, and ultrasonic signals from the
subject are discriminated using a filter for each vibration mode, and then each vibration mode
The output is appropriately selected and time-corrected and then polymerized, so that an
ultrasonic signal with a good S / N ratio can be extracted without impairing the real-time
property. Hereinafter, embodiments of the present invention will be described in detail with
reference to the drawings. FIG. 1 is a view for explaining a resonance mode of an ultrasonic
transducer, FIG. 2 is a view showing one embodiment of the present invention in a block diagram,
and FIG. 3 is a block described in FIG. It is the figure which showed the waveform of the
ultrasonic signal of the principal part of the figure. FIG. 1 shows the frequency spectrum of each
vibration mode of the ultrasonic transducer, and the horizontal axis shows frequency f and the
vertical axis shows transmission / reception level. In addition to the frequency f1 of the
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fundamental resonance mode, it is an odd number. Next resonance mode f3. F5. It can be
understood that it has one. Next, with reference to FIG. 3, the present invention will be described
in detail by FIG.
In this figure, 1 is an ultrasonic drive circuit (a, b, c) which outputs a drive signal having
frequency characteristics of each resonance mode, 2 is a power amplifier, 3 is an amplifier, 4 is a
band pass filter (A. B, C), 5 are combining devices, 51 is a delay circuit, 52 is a combining circuit,
and 6 is a narrow band transducer. 7 is a subject, 8 is a changeover switch. Now, the ultrasonic
drive circuit (a, b, c) 1 is a drive signal having frequency characteristics of each resonance mode,
and the changeover switch 8 substantially simultaneously (in fact, slightly deviated in time) a, b ,
C, the ultrasonic transducer 6 is excited and an ultrasonic pulse is sent to the subject 7, the
ultrasonic signal from the subject 7 is transmitted to each vibration mode fl, f2. F3 mixed
ultrasound signals, but with band pass filters (A, B, C), ultrasound signals a ′ ′, b ′ in each
vibration mode. It is separated into C ". [Refer to FIG. 3 (b)] These signals are corrected, for
example, by the delay circuit 51 so that the ultrasonic signals from the same sample overlap, and
added by the synthesis circuit 52 without losing the real time. , S / N ratio can also be improved.
As the addition method in the synthesis circuit 52, the detection output of the ultrasonic signals a
'to C ° in each resonance mode is added, or each ultrasonic signal a' to C 'is converted into a
constant frequency and added. There is a way to match. The signal waveforms of each part of the
above operation are shown in FIG. 3, (a) shows the output waveform of the power amplifier 2,
and (1) shows each output waveform of the band pass filters (A, B, C) 4 a ′ to C ° are the
output waveforms of the delay circuit 51. And (C) shows the frequency spectrum of the drive
pulses a, b and c. As apparent from this figure, the ultrasonic signals a 'to C' from the subject 7 in
each vibration mode are matched to the same timing by passing through the delay circuit 51, so
that the simple circuits can It is possible to add and remove ultrasonic signals. In contrast to the
conventional method where ultrasonic signals of the same frequency are sent to the subject a
plurality of times and their reflected signals are polymerized to obtain an improvement in the S /
N ratio, the present invention provides a single ultrasonic transformer. By using the vibration
characteristics of the zeroth-order resonance mode of the laser, ultrasonic pulses in a plurality of
vibration modes are transmitted with a slight time delay, and the reflection signal from the
subject is corrected by the delay circuit, It is characterized in that ultrasonic signals of different
frequencies of each vibration mode are polymerized at the same timing, and ultrasonic signals of
each vibration mode are transmitted almost at the same time. An improvement in the S / N ratio
is also obtained.
In addition, since no broadband transducer is required in this method, the efficiency of
transmission and reception is good, and by combining ultrasonic signals of each vibration mode
as appropriate, the same function as the broadband transducer can be obtained. (Effect of the
Invention As described above in detail, in the ultrasonic apparatus according to the present
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invention, the ultrasonic wave l · transducer can be used to generate the nth (generally n is an
odd number) resonance mode in addition to the fundamental resonance mode Focusing on the
fact that the narrow band transducer has better transmission and reception efficiency compared
to the wide band transducer, the narrow band transducer uses the transducer to shift slightly in
time, so that multiple vibration modes can be used. The acoustic pulse is sent to the subject, the
ultrasonic signal from the subject is discriminated using a filter for each vibration mode, and then
the output for each vibration mode is appropriately selected and polymerized. Since it is possible
to operate in a wide band, it is possible to transmit and receive an ultrasonic signal with high
efficiency without loss of real time property, and if the frequency characteristic of the object is
flat, the S / N ratio close to the theoretical value (Drive in n vibration modes When there is an
effect that can be extracted by n the% th power of).
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a view for explaining a resonance mode of an ultrasonic transducer, FIG. 2 is a view
showing an embodiment of the present invention in a block diagram, and FIG. 3 is a main part of
the block diagram described in FIG. Is a diagram showing the waveform of the ultrasonic signal
of FIG.
In the drawings, 1 is an ultrasonic drive circuit (a, b). c) and 2 are power amplifiers, 3 is an
amplifier, 4 is a band pass filter (A, B, C), 5 is a combining device, 51 is a delay circuit, 52 is a
combining circuit, and 6 is a transducer. 7 is the subject, fl, f2. F3 represents the center
frequency of each resonance mode.
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