JPH02136131A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To perform the generation and compression of a chirp wave by simple and inexpensive constitution by laminating an ultrasonic wave delay substance to an ultrasonic vibrator and properly distributing the thickness of said substance. CONSTITUTION:An ultrasonic probe 1 is formed by successively laminating an ultrasonic vibrator 3, an ultrasonic wave delay substance 4 and a matching layer 5 to a damper layer 2. The ultrasonic vibrator 3 is constituted so that the thickness in the direction going toward the ultrasonic wave delay substance 4 from the damper layer 2, that is, the thickness in a vibration direction is changed linearly and connected to a drive circuit and a receiving signal processing circuit through a coaxial cable 6. The ultrasonic wave delay substance 4 is constituted so as to be thin at the thick part of the ultrasonic vibrator 3 and thick at the thin part of said vibrator corresponding to the thickness in the vibration direction of the vibrator 3 and linearily changed in its thickness in the same way as the vibrator 3. By this constitution, the generation of an ultrasonic chirp wave and the compression of a receiving chirp wave due to pulse driving can be performed by the ultrasonic probe 1 itself without providing a pulse stretching circuit or a pulse compression circuit separately.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an ultrasonic probe.

[Conventional technology]

In recent years, as an ultrasonic diagnostic device, for example,
As disclosed in Japanese Patent No. 14 and Japanese Patent No. 63-8782, it has been proposed to use chirp waves whose frequency changes over time as ultrasonic waves.

[Problem to be solved by the invention]

However, in the conventional ultrasonic diagnostic apparatus described above, when transmitting ultrasonic waves, a pulse expansion circuit, a voltage controlled oscillator (VCO), and a surface acoustic wave filter (SAW filter) are used.
etc. to create a linearly changing signal, drive the ultrasonic transducer to generate a chirp wave, and when receiving, the chirp signal received by the ultrasonic transducer is pulse compressed using a SAW filter etc. I try to do that. Therefore, there is a problem that the circuit configuration becomes complicated and expensive.

This invention was made in view of these conventional problems, and an object of the present invention is to provide an ultrasonic probe that can generate and compress chirp waves with a simple and inexpensive configuration. do.

[Means and effects for solving the problem] In order to achieve the above object, the ultrasonic probe of the present invention includes an ultrasonic transducer whose thickness in the vibration direction varies depending on the position of the ultrasonic emission surface, and an ultrasonic delay material that is laminated on the ultrasonic emission surface of the ultrasonic transducer and provides different amounts of delay in accordance with the thickness distribution of the ultrasonic transducer; and by driving the ultrasonic transducer in pulses. Generating an ultrasonic chirp wave whose frequency changes over time via the ultrasonic delay material and projecting it onto the subject, and receiving the reflected wave from the subject by the ultrasonic transducer via the ultrasonic delay material. The configuration is such that pulse compression can be performed by doing this.

〔Example〕

FIG. 1 shows a first embodiment of the invention. This ultrasonic probe 1 includes an ultrasonic transducer 3 on a damper layer 2,
The ultrasonic delay material 4 and the matching layer 5 are sequentially laminated. The ultrasonic vibrator 3 is configured so that the thickness in the direction from the damper layer 2 toward the ultrasonic delay material 4, that is, the thickness in the vibration direction, changes linearly, and is connected to a drive circuit (not shown) and a receiver via a coaxial cable 6. Connect to signal processing circuit.

Further, the ultrasonic delay material 4 has a thickness that corresponds to the thickness of the ultrasonic vibrator 3 in the vibration direction, such that it is thinner in thicker parts of the vibrator 3 and thicker in thinner parts. Similarly, it is configured to vary linearly. Note that the damper layer 2 holds the ultrasonic transducer 3 and also
The matching layer 5 is configured to rapidly attenuate the vibrations of the object and emit short ultrasonic waves, and the matching layer 5 is configured to rapidly attenuate the vibration of
and the ultrasonic delay material 4 in order to match their acoustic impedances.

In the above configuration, when a pulse voltage is supplied to the ultrasonic transducer 3 from the drive circuit (not shown) via the coaxial cable 6, the ultrasonic transducer 3 emits ultrasonic waves with a frequency determined by its thickness as shown in FIG. 2A. The output is as shown. Here, the ultrasonic waves output from the ultrasonic transducer 3 are
Depending on the thickness, there are many high frequency components in thinner parts,
In thicker parts, there are many low frequency components. The ultrasonic waves emitted from the ultrasonic transducer 3 are delayed by the ultrasonic delay material 4 according to its thickness. In this embodiment, the thickness of the ultrasonic delay material 4 is made thinner in the thicker parts of the ultrasonic vibrator 3 and thicker in the thinner parts.
High frequency signals are delayed more than low frequency signals. Therefore, the ultrasonic wave emitted from the ultrasonic transducer 3 passes through the ultrasonic delay material 4 and becomes a chirp wave as shown in 2l8. radiated to the specimen.

Here, the chirp wave shown in 2l8 is radiated to the subject.
rx(t) is expressed as follows, where ω: changing frequency, Lw: delay time due to frequency ω, STF: lowest frequency, SPF: highest frequency, and t: time.

The ultrasonic wave emitted to the object is reflected by a slight difference in acoustic impedance within the object, and the reflected chirp wave (C in FIG. 2) is transmitted again to the matching layer 5 and the ultrasonic delay material 4.
It enters the ultrasonic transducer 3 through the . At this time, Fig. 2C
The reflected chirp wave shown in FIG. 2 is pulse-compressed because the reflected chirp wave that reaches the high frequency side of the ultrasonic transducer 3 is further delayed by the ultrasonic delay substance 4, and the received signal output from the ultrasonic transducer 3 is pulse-compressed. As shown in the figure, the pulse width is approximately the same as the wabo drive pulse width.

Here, the received signal R, (
t) is expressed as. Note that ω in equation (2), STF,
SPF and t represent the same things as in equation (1).

In addition, T, (L) and R, ( shown in FIGS. 2B and C)
t) is STF = 7! , 1llz, SPF=14Mfl
z represents the waveform when the maximum delay time (w□X=78 nsec).

The received signal pulse-compressed as described above and output from the ultrasonic transducer 3 is supplied to a not-shown received signal processing circuit via the coaxial cable 6, processed, and displayed on a monitor.

As described above, according to this embodiment, the ultrasonic probe l itself generates ultrasonic chirp waves by pulse driving and compresses the received chirp waves without providing a separate pulse expansion circuit or pulse compression circuit. This allows ultrasonic diagnostic equipment to be made simple and inexpensive.

FIG. 3 shows a second embodiment of the invention. This ultrasonic probe 11 is configured to mechanically radially scan ultrasonic waves, and has first to third electro-acoustic transducers 1.
2-1 to 12-3. First electro-acoustic converter 1
2-1 corresponds to the ultrasonic transducer 3 having a linearly varying thickness on the damper layer 2, similar to the ultrasonic probe 1 shown in FIG. 1, and the thickness of this ultrasonic transducer 3. an ultrasonic retardation material 4 and a matching layer 5 having a thickness that varies linearly.
are sequentially stacked and a pulse voltage is supplied from a drive circuit (not shown) via a coaxial cable 6 connected to the ultrasonic transducer 3, thereby emitting chirp waves and pulse-compressing the received chirp waves. Then, the received signal is supplied to a received signal processing circuit (not shown) via the coaxial cable 6.

The second electro-acoustic converter 12-2 is configured by sequentially laminating an ultrasonic transducer 14 of a constant thickness and a matching layer 15 on a damper layer 13, and the matching layer 15 is used as the first electro-acoustic converter. It is provided so as to be rotatable about the vibration direction of the ultrasonic transducer 14 with respect to the first electro-acoustic transducer 12-1, facing the matching layer 5 of the section 12-1. Note that the matching layer 5 and the matching layer 15
An ultrasonic transmitting substance 16 is filled between the two. Also,
The third electro-acoustic transducer 12-3, like the second electro-acoustic transducer 12-2, has an ultrasonic transducer 18 of a constant thickness and a matching layer 19 sequentially laminated on the damper layer 17. The matching layer 19 serves as the second electro-acoustic transducer 12.
- mechanically connected to the second electro-acoustic transducer 12-2 so as to face outward perpendicular to the rotation axis of the second electro-acoustic transducer 12-2 so as to rotate together with the second electro-acoustic transducer 12-2; 18 to the second electrical-acoustic converter 12- via the coaxial cable 20.
It is electrically connected to the ultrasonic transducer 14 of No. 2.

In this embodiment, the first electro-acoustic converter 12-1
The ultrasonic chirp wave emitted from the is converted into an electrical signal by the second electro-acoustic converter 12-2, and then supplied to the third electro-acoustic converter 12-3 via the coaxial cable 20. , here, it is again converted into an ultrasonic chirp wave and projected onto the subject via the matching layer 19. In addition, the reflected wave of the ultrasonic chirp wave from the object is converted into a third electro-acoustic conversion f
1512-3 converts it into an electrical signal and sends it to the coaxial cable 20
is supplied to the second electro-acoustic converter 12-2 via
Here, after being converted into an ultrasonic chirp wave, the first electricity -
The received signal is received by the acoustic converter 121 and pulse-compressed, and the received signal is supplied to a not-shown received signal processing circuit via the coaxial cable 6 and displayed on a monitor. therefore,
Second and third electro-acoustic converters 12-2 and 12
-3 is rotated integrally with the first electro-acoustic transducer 12-1, so that the subject can be radially scanned by ultrasonic waves. In addition, the second. Third electro-acoustic converter 12-2. Damper layer 13 configuring 12-3.
17 act to suppress the generation of unnecessary ultrasonic waves during electro-acoustic conversion by the ultrasonic transducers 14 and 18, respectively.

According to this embodiment, since the subject can be radially scanned, it is particularly suitable for use by being inserted into a body cavity. In addition,
In the first embodiment as well, the ultrasonic probe 1 can be configured to be rotatable in a direction orthogonal to the vibration direction of the ultrasonic transducer 3 to perform radial scanning.

〔Effect of the invention〕

As described above, according to the present invention, by laminating ultrasonic retardation materials on an ultrasonic transducer and appropriately distributing the thickness of these materials, it is possible to generate chirp waves by using an ultrasonic probe alone. Now that it is possible to perform pulse expansion and pulse compression to compress the received chirp,
An ultrasonic diagnostic device using chirp waves can be made simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the invention, and FIGS. 2A-D
is a signal waveform diagram for explaining its operation, and FIG. 3 is a diagram showing a second embodiment of the present invention. l... Ultrasonic probe 2... Damper layer 3...
・Ultrasonic transducer 4...Ultrasonic delay material 5...Matching layer 6...Coaxial cable

Claims (1)

[Scope of Claims] 1. An ultrasonic transducer whose thickness in the vibration direction varies depending on the position of the ultrasonic emission surface, and an ultrasonic transducer laminated on the ultrasonic emission surface of the ultrasonic transducer, the thickness of the ultrasonic transducer and an ultrasonic delay material that provides different delay amounts depending on the distribution, and by driving the ultrasonic transducer in pulses, an ultrasonic chirp wave whose frequency changes with time is generated through the ultrasonic delay material. 1. An ultrasonic probe, characterized in that the ultrasonic probe is configured to be capable of pulse compression by projecting a wave onto a subject and receiving the reflected wave from the subject via the ultrasonic delay material and the ultrasonic transducer.