JPH0477272B2

JPH0477272B2 -

Info

Publication number: JPH0477272B2
Application number: JP57000347A
Authority: JP
Inventors: Toshio Ogawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1982-01-06
Filing date: 1982-01-06
Publication date: 1992-12-07
Also published as: JPS58118972A

Description

【発明の詳細な説明】本発明は超音波撮像装置、特に方位分解能を向
上せしめた超音波撮像装置に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic imaging device, and particularly to an ultrasonic imaging device with improved lateral resolution.

超音波撮像装置の性能は探触子の指向特性（ビ
ーム幅、サイドローブレベル）とパルス特性によ
り、ほば決定される。すなわち、ビーム幅は方位
分解能に、パルス特性は距離分解能に関連する。
近距離音場の主ビーム幅を狭める目的で通常、配
列素子方向（長軸方向）の各素子の位相制御によ
り凹面収束をかける方法がとられている。しか
し、この凹面収束法は焦域では回折限界の主ビー
ム幅が得られるが、その前後ではかえつて悪化す
る欠点があつた。それに対し、長軸方向の配列素
子数を制御することにより、口径変化させること
により、焦域より近傍のビーム特性を改善させ
る、いわゆる、可変開口方式や、受波収束を各深
度ごとに行う、いわゆる、ダイナミツクフオーカ
ス方式などがある。このようにして、配列素子の
長軸方向の超音波ビームはぼぼ理論的な値が得ら
れている。 The performance of an ultrasonic imaging device is largely determined by the directional characteristics (beam width, sidelobe level) and pulse characteristics of the probe. That is, the beam width is related to lateral resolution, and the pulse characteristics are related to distance resolution.
In order to narrow the main beam width of the near-field sound field, a method is usually used to apply concave convergence by controlling the phase of each element in the array element direction (long axis direction). However, although this concave convergence method can obtain a diffraction-limited main beam width in the focal region, it has the disadvantage that it actually gets worse before and after that. On the other hand, the so-called variable aperture method improves the beam characteristics in the vicinity of the focal region by controlling the number of array elements in the long axis direction and changing the aperture. There is a so-called dynamic focus method. In this way, the ultrasonic beam in the long axis direction of the array element has approximately a theoretical value.

しかし、配列方向（長軸方向）と直交する短軸
方向のフオーカスについては、第１図ａに示すよ
うな凹面の音響レンズを前面に付加する方法がと
られている。この音響レンズ方式は後でも説明す
るように、第１図ｂの実線で示す短軸長Ｄ、収束
点r₃の凹面収束の固定収束であるため、前述の長
軸方向の凹面収束と同一の理由で、焦域の前後の
ビーム特性は悪い。しかし、短軸方向のダイナミ
ツクフオーカスを電子的制御するためには、２次
元配列素子および多数の遅延線素子を必要とす
る。また、音響レンズの曲率を機械的に変化させ
る方式は振動による耐久性などに問題がある。 However, for focusing in the short axis direction perpendicular to the arrangement direction (long axis direction), a method of adding a concave acoustic lens to the front surface as shown in FIG. 1a has been adopted. As will be explained later, this acoustic lens system has fixed convergence of the short axis length D and the convergence point _r3 shown by the solid line in Fig. 1b, so it is the same as the concave convergence in the long axis direction mentioned above. For this reason, the beam characteristics before and after the focal region are poor. However, in order to electronically control the dynamic focus in the short axis direction, a two-dimensional array element and a large number of delay line elements are required. Furthermore, the method of mechanically changing the curvature of the acoustic lens has problems with durability due to vibration.

一方、素子配列と直交方向（短軸方向）の口径
の制御については特開昭56−18778号公報に記載
されている。しかしながら、ここに記載されてい
るのは、圧電体をはさんで対向する信号側電極と
接地側電極とを互いに直交する方向に分割し、外
部に設けた選択スイツチによ分割された接地電極
を選択的に接地する構成であり、開口制御のため
の外部スイツチが必要であること、信号側電極は
短軸方向には一様であり分割されていないため短
軸方向の信号の分離が不可能であり、可変収束点
とできないことなどの欠点を有する。 On the other hand, control of the aperture in the direction (minor axis direction) perpendicular to the element arrangement is described in Japanese Patent Laid-Open No. 18778/1983. However, what is described here is that the signal-side electrode and the ground-side electrode, which face each other with a piezoelectric material in between, are divided in directions orthogonal to each other, and the divided ground electrode is connected to the divided ground electrode using an external selection switch. The configuration is selectively grounded, requiring an external switch for aperture control, and the signal side electrode is uniform in the short axis direction and is not divided, making it impossible to separate signals in the short axis direction. However, it has drawbacks such as the inability to have a variable convergence point.

そこで、本発明は簡略な構成により短軸方向の
可変口径を実現することにより、高性能超音波撮
像装置を提供することを目的とする。 Therefore, an object of the present invention is to provide a high-performance ultrasonic imaging device by realizing variable aperture in the short axis direction with a simple configuration.

以下、本発明を詳細に説明する。 The present invention will be explained in detail below.

第１図ａは本発明の全体説明図であり、１，
２，…、Ｎは長軸方向のＮ個の配列素子、１，
２，…、Ｍは短軸方向のＭ個の電極分割数、Ｄは
短軸最大長、r₂，r₄は短軸長さの切換点、r₁，r₃
は収束点である。ここで、送波は短軸固定音響レ
ンズ、受波は短軸可変口径について説明する。深
度０〜r₂区間では短軸長D/2、収束点r₁、深度r₂
〜r₄区間では短軸長Ｄ、収束点r₃、深度r₄〜区間
では短軸長2/3Ｄ、収束点r₃、とする。 FIG. 1a is an overall explanatory diagram of the present invention, and 1,
2,...,N are N array elements in the long axis direction, 1,
2,..., M is the number of M electrode divisions in the short axis direction, D is the maximum length of the short axis, r ₂ , r ₄ are the switching points of the short axis length, r ₁ , r ₃
is the convergence point. Here, a short-axis fixed acoustic lens will be used for transmitting waves, and a short-axis variable aperture will be used for receiving waves. In the depth 0 to r ₂ section, short axis length D/2, convergence point r ₁ , depth r ₂
In the ~ _r4 section, the short axis length is D and the convergence point _r3 , and in the depth _r4 ~ section, the short axis length is 2/3D and the convergence point _r3 .

第１図ｂの実線は短軸長Ｄ、収束点r₃の凹面収
束の場合の−20dB超音波ビーム幅であり、同図
点線は短軸可変口径方式の−20dB超音波ビーム
幅である。 The solid line in FIG. 1b is the -20 dB ultrasonic beam width in the case of concave convergence with short axis length D and convergence point _r3 , and the dotted line in the figure is the -20 dB ultrasonic beam width in the short axis variable aperture method.

このように本発明である短軸可変口径による効
果は著るしいものがある。 As described above, the effect of the short axis variable aperture according to the present invention is remarkable.

第２図ａは本発明に係る短軸可変口径の一実施
例を示す図であり、PZTは圧電変換素子、手前
が電極PE、反対側は電極NEである。各配列
素子Ｎ＝１、２、３は分離されているか、または
構が切られており、相互のカツプリングが除去さ
れる。短軸方向は圧電素子は分割されておらず、
電極PEはＭ＝１、２、…、７個に分割されて
いる。ここで短軸方向に分割されていても問題な
いことは明らかである。ここで電極の寸法とし
ては超音波周波数3.5MHzで約１mm×１mm程度で
ある。この短軸方向に分割された電極PEの一
部（第２図ａのPEPで示す部分）は第２図ｂに
示すようなIC化されたスイツチSWからなつてい
る。 FIG. 2a is a diagram showing an embodiment of the short axis variable aperture according to the present invention, in which PZT is a piezoelectric transducer, the front side is the electrode PE, and the opposite side is the electrode NE. Each array element N=1, 2, 3 is separated or disconnected, eliminating mutual coupling. The piezoelectric element is not divided in the short axis direction,
The electrode PE is divided into M=1, 2, . . . 7 electrodes. It is clear that there is no problem even if it is divided in the short axis direction. Here, the dimensions of the electrode are approximately 1 mm x 1 mm at an ultrasonic frequency of 3.5 MHz. A part of the electrode PE divided in the short axis direction (the part indicated by PEP in FIG. 2a) is made up of an IC switch SW as shown in FIG. 2b.

第２図ｂにおいて、Ｄはダイオード、R₁，R₂
は抵抗、Ｃはコンデンサ、１０は電極PEとダ
イオードの接続点、１１は制御信号C₁〜C₇と抵
抗R₁の接続点、１２はコンデンサＣと送受波器
の接続点、１３は抵抗R₃と接地点の接続点であ
る。また制御信号C₁〜C₇の例を第４図に示す。 In Figure 2b, D is a diode, R ₁ , R ₂
is a resistor, C is a capacitor, 10 is a connection point between the electrode PE and the diode, 11 is a connection point between the control signals C ₁ to C ₇ and the resistance R ₁ , 12 is a connection point between the capacitor C and the transducer, and 13 is a resistance R This is the connection point between ₃ and the ground point. Further, an example of the control signals C ₁ to C ₇ is shown in FIG. 4.

即ち、送波信号は負の高圧パルスであり、低圧
の制御信号の有無に関係なくダイオードＤを通過
し、電極に印加される。この結果、電極PEの
全ての分割部分（第１図で示す口径Ｄに相当する
範囲）から超音波が凹面音響レンズを介して送波
される。一方、受波信号は制御信号の電圧が1V
のときダイオードＤはONとなり受波信号は受波
器へ出力するが制御信号の電圧が−1Vのときダ
イオードＤはOFFとなり、受波信号は出力され
ない。すなわち、制御信号により、受名器信号を
ON、OFFするスイツチが構成されている。 That is, the transmission signal is a negative high voltage pulse, which passes through the diode D and is applied to the electrode regardless of the presence or absence of the low voltage control signal. As a result, ultrasonic waves are transmitted from all divided portions of the electrode PE (range corresponding to the aperture D shown in FIG. 1) via the concave acoustic lens. On the other hand, the received signal has a control signal voltage of 1V.
When , diode D is turned ON and the received signal is output to the receiver, but when the voltage of the control signal is -1V, diode D is turned OFF and the received signal is not output. In other words, the control signal controls the name receiver signal.
It consists of a switch that turns on and off.

第４図を以下により詳細に説明する。第４図に
示す制御信号C₁〜C₇により超音波ビームを短軸
方向に可変口径制御して深度方向で収束点の位置
を変化させることを示している。第４図の例で
は、ある深度までは、制御信号C₄，C₃，C₅の電
圧が1Vに制御され、短軸方向の中央部にある分
割部分３，４，５の受波信号が受波器へ出力され
る。次の深さでは、制御信号C₄，C₃，C₅，C₂，
C₆の電圧が1Vに制御され、短軸方向の中央部に
ある分割部分３，４，５，２，６の受波信号が受
波器へ出力される。さらに次の深度では、制御信
号C₁〜C₇の電圧が1Vに制御され、短軸方向の全
ての分割部分の受波信号が受波器へ出力される。
さらにもつと深い深度では、順次、制御信号C₄，
C₃，C₅，C₂，C₆の電圧、制御信号C₄，C₃，C₅の
電圧が1Vに制御され、各深度領域で超音波ビー
ムが異なる形状を有するように各短軸方向の分割
部分が制御され、短軸方向の深度による超音波ビ
ーム形状を電子的に制御することが可能となる。
後で説明するように電極NE側には第１図に示す
凹面音響レンズが装着されるので、この音響レン
ズによる超音波の収束効果と、短軸方向での口径
の変化を電子的に制御することにより、短軸方向
の深度による超音波ビーム形状を改善するもので
ある。本発明の短軸可変口径の効果は前記したよ
うに著しい。 FIG. 4 will be explained in more detail below. The control signals C ₁ to _{C 7} shown in FIG. 4 are used to control the aperture of the ultrasonic beam in the short axis direction to change the position of the convergence point in the depth direction. In the example shown in Fig. 4, the voltages of control signals C ₄ , C ₃ , and C ₅ are controlled to 1V up to a certain depth, and the received signals of divided portions 3, 4, and 5 at the center in the short axis direction are Output to the receiver. At the next depth, the control signals C ₄ , C ₃ , C ₅ , C ₂ ,
The voltage of C ₆ is controlled to 1V, and the received signals of the divided portions 3, 4, 5, 2, and 6 located at the center in the short axis direction are output to the receiver. Furthermore, at the next depth, the voltages of the control signals C ₁ to C ₇ are controlled to 1V, and the received signals of all the divided portions in the short axis direction are output to the receiver.
At even greater depths, the control signals C ₄ ,
The voltages of C ₃ , C ₅ , C ₂ , and C ₆ and the voltages of control signals C ₄ , C ₃ , and C ₅ are controlled to 1V, and each short axis direction is adjusted so that the ultrasound beam has a different shape in each depth region. It is possible to electronically control the ultrasonic beam shape depending on the depth in the short axis direction.
As will be explained later, the concave acoustic lens shown in Figure 1 is attached to the NE side of the electrode, so the convergence effect of the ultrasound by this acoustic lens and the change in aperture in the short axis direction are electronically controlled. This improves the ultrasonic beam shape depending on the depth in the short axis direction. The effect of the short axis variable aperture of the present invention is remarkable as described above.

第２図ａに示すような制御信号は各配列素子に
ついて反応する電極の接続点１１を長軸方向に
接続し、送受波信号は各配列素子について電極
の接続点１２を短軸方向に接続する。 The control signal as shown in FIG. 2a connects the connection points 11 of the electrodes that react for each array element in the long axis direction, and the transmission/reception signal connects the connection points 12 of the electrodes for each array element in the short axis direction. .

第２図におけるスイツチSWのチツプ面積はコ
ンデンサ容量が主要なものであり、例えば容量が
1000pF程度となるとチツプ面積は１mm×１mm程
度となるので第３図に示すように電極の大部分
にコンデンサが形成されることになる。 The chip area of the switch SW in Figure 2 is mainly due to the capacitor capacity.
If it is about 1000 pF, the chip area will be about 1 mm x 1 mm, so a capacitor will be formed on most of the electrodes as shown in FIG.

第２図及び第３図において電極NE側は第１
図の音響レンズが接着され、電極PE側は音響
パツキングが接着される。また、電極NEと音
響レンズの中間にλ／４層などの整合層が入つて
も問題ない。 In Figures 2 and 3, the electrode NE side is the first
The acoustic lens shown in the figure is glued, and the acoustic packing is glued to the PE side of the electrode. Further, there is no problem even if a matching layer such as a λ/4 layer is inserted between the electrode NE and the acoustic lens.

また、第２図及び第３図において、IC化され
たスイツチは、この構成に限ることはないことは
明らかであり、例えば、高耐圧MOSスイツチな
どでもよい。 Furthermore, in FIGS. 2 and 3, it is clear that the IC-based switch is not limited to this configuration; for example, it may be a high-voltage MOS switch.

以上は受波短軸可変口径について述べたので、
制御信号電圧は高々1V程度でよい。 The above is about the receiving wave short axis variable aperture, so
The control signal voltage may be about 1V at most.

しかし、送波についても短軸可変口径するため
には、制御信号電圧は負の高電圧（例えば−
200V）とする。 However, in order to make the short axis variable aperture for wave transmission, the control signal voltage must be set to a negative high voltage (for example -
200V).

送波信号が負の高圧パルスあるいは正負を含ん
だパルスである時、送波信号の負の電圧（例えば
−100V）より絶対値のより大きい負の電圧（例
えば−200V）を制御信号として用いることによ
りダイオードＤは遮断されるので、超音波ビーム
を短軸方向の口径を変化して送波することができ
る。 When the transmission signal is a negative high voltage pulse or a pulse containing positive and negative signals, use a negative voltage (e.g. -200V) with a larger absolute value than the negative voltage (e.g. -100V) of the transmission signal as the control signal. Since the diode D is blocked by this, the ultrasonic beam can be transmitted while changing the aperture in the short axis direction.

以上述べたように、本発明によれば配列振動子
の短軸可変口径が可能となり、高性能超音波撮像
装置に寄与する所が大きい。 As described above, according to the present invention, variable aperture of the short axis of the array transducer becomes possible, which greatly contributes to high-performance ultrasonic imaging devices.

[Brief explanation of the drawing]

第１図は本発明の概略説明図、第２図及び第３
図は本発明の一実施例の構成を示す図、第４図は
制御信号の例であるを示す図である。 Figure 1 is a schematic explanatory diagram of the present invention, Figures 2 and 3.
This figure shows the configuration of an embodiment of the present invention, and FIG. 4 is a diagram showing an example of control signals.

Claims

[Claims] 1. A plurality of piezoelectric transducers each having electrodes on both sides are arranged in an array in one direction, and each piezoelectric transducer transmits a transmission signal from a wave transmitting/receiving circuit or a receiving signal to the wave transmitting/receiving circuit. In an ultrasonic probe provided with a signal line for transmitting signals, an electrode on at least one surface of each piezoelectric transducer is divided into a plurality of positions along a direction perpendicular to the arrangement of the piezoelectric transducer array. , a plurality of individual signal electrodes are formed for each piezoelectric transducer, and each individual signal electrode is connected to the signal line via a switch element, and the switch element connects each piezoelectric transducer to the signal line. By opening and closing the electrical connection between the signal line and the separate signal electrode, the aperture of the wave transmission and/or reception in the short axis direction, which is the direction perpendicular to the arrangement of the piezoelectric transducer array, is changed and the ultrasonic wave is An ultrasonic probe characterized by transmitting and/or receiving waves. 2. A switch element connected to each of the individual signal electrodes located at the same position in the short axis direction of each of the piezoelectric transducers and a control line connected in the arrangement direction of the piezoelectric transducer array, 2. The ultrasonic probe according to claim 1, wherein the switch element is opened and closed by a control signal applied to the control line. 3. The ultrasonic probe according to claim 1, wherein an acoustic lens is provided on a surface opposite to the surface having the individual signal electrodes.