JPH0466578B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a receiving phaser for an electronic scanning ultrasonic tomography apparatus.

[Prior art]

As a conventional receiving phaser, there is a receiving phaser including a pre-delay means for phasing a received signal having a minute delay time and a main delay means for phasing a received signal having a relatively long delay time. An example thereof is described in Japanese Patent Application Laid-Open No. 53-28989. Here, as the delay means, an analog LC delay line, a charge phase shift element, a digital memory, etc. are usually used.

Furthermore, it has not been possible to switch the predelay means during the reception period because switching noise occurs.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reception phaser that enables dynamic focusing by switching the pre-delay means according to the convergence point of the ultrasound beam during the reception period.

[Summary of the invention]

In order to achieve such an object, the present invention includes a main delay means having a holding means and a storage means, and synchronizes the switching time of the pre-delay means with the holding time of the holding means, and By holding the signal at the time when the switching noise disappears using the holding means, the influence of the switching noise is removed, the signal is stored in the storage means, and the received signal is phased.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is an explanatory diagram of the reception dynamic focus, where T ₁ , T ₂ , ..., T _o are each element of the array transducer, R ₁ and R ₂ are the depths, and A _i , B _i (i= 1, 2,...,
n) are the straight line and arc OA⌒ connecting each element to the depths R ₁ and R ₂
The intersection with i and OB⌒i appears. Here, arc OA⌒i,
OB⌒i has centers R ₁ and R ₂ and radii ₁ and ₂ , respectively.
It is the arc of the circle. In order to perform reception dynamic focus, during the reception period after transmitting one ultrasonic pulse, the reflected waves at a shallow depth gradually reach the element at deeper depths. It is necessary to sequentially switch the focus point of the receiving phaser. For example, in order to phase the received signal from a depth R ₁ , the array element T ₁ compensates for the delay time corresponding to the distance _{1 1} , and in order to phase the received signal from the depth R ₂ , the array element T 1 compensates for the delay time corresponding to the distance 1 1. It is necessary to compensate for the delay time corresponding to a distance of ₁ B ₁ .

_{Here , since 1 1 > 2 2 > 3 3 , the} predelay _{means and T} By having a main delay means corresponding to ₃ A ₃ , a receiving phaser can be realized.

In order to perform reception dynamic focus, the pre-delay means and the main delay means may be controlled so that the reception beam converges at each depth.

FIG. 2 shows an embodiment of the present invention, 1, 2,...,
n is an array element, 10-2...10-(n-1) is a pre-delay element, 11-1...11-m is a holding circuit, 12-1...12-m is a main delay element, 13-
1...13-m is a pre-delay adder, 19-1...
...19-m is the output of the main delay, 20 is the adder, 30
is the receiver phaser output terminal. However, m=n/3
(m: positive integer). Here, the circuit up to the adder 13 will be referred to as pre-delay means, and the portions thereafter will be referred to as main delay means. Here, it is known that the delay time τ ₁ between the elements of the pre-delay element is given by τ ₁ =dsin θ/c (1) from the element pitch d, the deflection angle θ, and the speed of sound c. In the case of Fig. 2, the predelay elements 10-2, 10-5,..., 10-
The delay time of (n-1) is τ ₁ calculated by equation (1) using the deflection angle θ from the position of each array element to the convergence point, and
Similarly, the delay time of 6,...,10-(n-2) is determined by the deflection angle θ from the position of each array element to the convergence point.
It is 2τ ₁ for τ ₁ calculated by equation (1) using .
Also, the delay time τ ₂ of the main delay element can be found from the drawing in Figure 1, but in reality, the received signal reaches the element at the center of the aperture first, so the received signal at the center of the aperture is transferred to the received signal at the outside of the aperture. It is necessary to delay the signal. In Fig. 2, the received signal of elements 1, 4, or n is the reference for compensation of minute delay time, so the delay amount of the pre-delay means is zero, and the delay line is connected to these element channels. However, since it is generally necessary to move the center position of the ultrasonic beam in the element arrangement direction, a delay line having a tap with zero delay amount is inserted in all element channels.

Although reception phasing is possible with the configuration shown in FIG. 2, the timing of switching the predelay during the reception period will be explained using FIGS. 3a and 3b.

Reference numeral 10 in FIG. 3A is a pre-delay element, such as a tapped inductance L and a capacitance C as a delay line. 14 is a multiplexer, α is a holding circuit 1
1 and a control signal for the main delay element 12. In other words, the signal value of the control signal α at each timing is sequentially sampled by the holding circuit 11 and held, and the storage circuit 12 sequentially shifts the value to the output side. β is a control signal for the multiplexer 14, and the tap switching of the delay line for changing the convergence point is performed at the timing of this control signal.
As shown in FIG. 3b, the control signal β is generated in synchronization with the control signal α, preceding the control signal α by a time τ (>0). Here, it is assumed that the switching noise completely disappears after τ time. In this way, even if the predelay is switched by the multiplexer 14 during the reception period,
The data held in the holding circuit 11 is not affected by switching noise.

Next, the number of times the predelay is switched during the reception period will be explained.

The predelay may be continuously switched depending on the convergence point of the received beam, but since the inter-channel directivity of the main delay means is relatively wide, the number of switches may be very small.

FIG. 4 shows an example of inter-channel directivity characteristics of the main delay means.

Now, as shown in Figure 2, due to the pre-delay, 3
When the input is 1 and the output is 1, the channel-to-channel directional characteristic of the main delay is expressed as
Corresponding to the case of = 1.92 mm, the first zero point θ ₀ is θ ₀ = sin ^-1 λ/3d = 13 degree (2). (Here, d = 0.64 mm and λ = 0.43 mm.) Since the main delay means has a wide inter-channel directivity characteristic as described above, it is only necessary to switch several points so that they overlap.

Therefore, as shown in FIGS. 1 and 4, for elements located far from the center of the array element, it is necessary to switch the directivity characteristics of the predelay three times in the order of , , , , , , , , , , , , .
On the other hand, the central array element does not need to be switched with its directional characteristics unchanged.

As shown in Figure 5, the receiving aperture D is centered symmetrically.
When divided into D ₁ , D ₂ , D ₃ , and D ₄ , at the receiving aperture of the outermost D ₄ , the control signal β ₄ of the predelay sequentially changes the directivity to ~. Partial diameter D ₃ , D ₂ , D ₁
are changed sequentially as shown in the figure, but the number of switching points decreases.

In the above explanation, the number of switching points is the receiving aperture,
It is clear that various modifications can be made depending on the depth and the configuration of the predelay.

Further, in the above description, a linear type vibrator is assumed, but the same applies to a convex type vibrator as shown in FIG. Here, R ₀ is the radius of curvature of the vibrator, and D is the total receiving aperture.

In Figure 6, the transducer T ₁ outside the receiving aperture
If the pre-delays of ~ _T3 are in phase, the inter-channel directivity characteristic of the main delay will be V. Since the receiving beam needs to be formed at the convergence point R, the outer transducer T ₁
It is necessary to control the predelay so that the directional characteristic of ~T ₃ is formed in the direction of .

〔Effect of the invention〕

In this way, even if the pre-delay is switched during the above period, the main delay operates without being affected by the switching noise, making reception dynamic focus possible and contributing to improved performance of the ultrasonic tomography device. The place is large.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 a is a diagram showing an embodiment of the present invention, FIG. 3 b is a diagram showing its operation, and FIG. Figure, 5th
The figure is a diagram for explaining the operation of the present invention, and FIG. 6 is a diagram showing the directivity characteristics of the predelay in a convex type vibrator. 10... Pre-delay element, 11... Holding circuit, 12...
Main delay element, 20...adder.

Claims (1)

[Claims] 1 Ultrasonic waves that are converged by receiving reflected waves generated by sending an ultrasonic pulse to a target by an array transducer, and controlling and adding the phases of each received signal from each element of the array transducer In a device that forms a beam to obtain an ultrasonic image, the array transducer is grouped into multiple adjacent elements, and a pre-delay compensates for the mutual minute delay time of received signals from each element in each group. and a first adding means for adding the received signals from the elements within the group whose minute delay times have been compensated for each group, respectively;
comprising a main delay means for compensating the mutual delay time of the added received signals of each group, and a second addition means for adding the received signals that have passed through the main delay means,
The pre-delay means each have a tap switching function and consist of a delay line provided for each element channel, while the main delay means each include a storage means that stores each sampled signal for a delay time and then continues the process. and the sampling in the main delay means is performed after a time elapses from the time when the pre-delay means is switched to switch the convergence point of the ultrasonic beam until the noise generated by the switch disappears. 1. An ultrasonic receiving phaser, comprising means for generating a control signal to the pre-delay means and the main delay means so as to control the pre-delay means and the main delay means.