JPH0575415B2 - - Google Patents

Description

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

[Background of the invention]

The configuration of a conventional receiving phaser will be explained below using the drawings. FIG. 1 represents a trapezoidal field of view of an ultrasonic tomography device. In the figure, sections 1 to 2 are linear sections, sections 3 to 4 to 5 are inclined sections with a deflection angle of θ, and 6 is a deflection angle of -θ.
represents one scanning line of the slope of .

In order to deflect the ultrasonic beam as shown in the figure, it is necessary to control the phase of the transmitted and received signals of each array element. FIG. 2a is a diagram showing a circuit configuration for phasing the received signal from the direction of the deflection angle θ.
1, 2, 3, ..., N are array elements, 10-1 to 1
0-N is a sample hold circuit, 11-1 is an adder, and 12-1 is an output terminal. C ₁ ~ _{C N} and
C _A is a control signal. AA′ is the receiving phase plane with the deflection angle θ, and in order to phase and add the input signals of each array element with the same phase, the input signal of the i-th element is delayed by (N-i)τ. After that, it is necessary to add the signals of all the elements. Here, τ is the delay time between elements, and is given by the following equation.

τ=dsinθ/v (1) Here, θ is the deflection angle, d is the element spacing, and v is the speed of sound.

In order to realize the signal delay as described above, sample and hold circuits 10-1 to 10- of each array element are used.
The control signal shown in FIG. 2b may be applied to N.
That is, the control signal C ₁ is the same as the timing of the transmission pulse, and the control signals C ₂ to C _N and C _A are
τ~(N-1)τ and _τA are delayed from _C1 , respectively. However, τ _A >(N-1) τ. The received signals input to each element 1 to N are held by sample and hold circuits 10-1 to 10-N at the timing of control signals C ₁ to C _N , respectively, and are sent to an adder 11.
-1 is added at the timing of C _A.

In the conventional receiving phaser configured as described above, the hold time (delay time) of the sample and hold circuit 10-i of the i-th element is (N-i)τ, and the maximum hold time (N- 1) τ must be less than or equal to the sampling period T. Therefore,
The inter-element delay is τ<T/N-1 (2), that is, the deflection angle θ is limited by the following equation.

θ<sin ^-1 vT/d(N-1) ...(3) Since the sampling period T is determined by the ultrasonic frequency, the deflection angle θ is limited by the number of array elements N, and when N is large, It is necessary to reduce θ. Therefore, it has been difficult to obtain a large trapezoidal field of view as shown in FIG. 1 with the conventional receiving phaser.

[Purpose of the invention]

The present invention was made in order to solve the problems of the conventional receiving phasing device.The phasing delay of each array element is configured with a sample and hold circuit, and the output signal of each sample and hold circuit is sequentially processed. It is an object of the present invention to provide an ultrasonic reception phasing circuit that can phase signals delayed longer than the sampling period by serial addition and obtain a large deflection angle.

[Summary of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3a is a diagram showing the configuration of a series addition type receiving phaser according to the present invention, and 13-2 to 13-N
is a two-input signal adder, and 15-2 to 15-N are fixed minute delay means for correcting the settling time of the sample and hold circuit.
A C delay line, a charge coupled device (CCD charge coupled device), etc. are used. The rest is the same as FIG. 2a.

In this configuration, the settling time of each sample and hold circuit is set to be equal to Δ. As shown in Figure 3b, when the deflection angle is 0° and the received signal is input to each element 1 to N at the same time, the signal of element 1 is processed by the sample and hold circuit 10-1 as shown in Figure 3c. Sample and hold is performed at the timing of control signal _C1 . The received signal of the element 2 is transmitted by the delay circuit 15-2 to the settling time Δ of the sample-hold circuit 10-1.
after a delay of
Sample and hold is performed at the timing of _C2 . Similarly, the received signal of element N is transmitted to delay circuit 15-
Depending on N, the sample and hold circuits 10-1 to 10-1
After being delayed by a settling time (N-1)Δ of 0 to (N-1), the signals are added by the adder 13-N, and then
It is sampled and held at the timing of C _N , and outputs the addition result of the in-phase received signals of each element to the output terminal 12-1.

When the deflection angle is θ, the sample and hold circuits 10-1 to 10-N may be controlled at the timing shown in FIG. 3d with the delay time between each element set as (τ+Δ). However, T is the sampling period, τ
is given by equation (1).

According to such a configuration, for example, the next sampling time of element 1 only needs to be delayed from the control signal C2 of sample hold circuit 10-2 of element ₂ by a minute time ΔT. Therefore, the limit on the delay time τ between each element is τ<T-Δ-ΔT...(4) Since Δ, ΔT<<T, the maximum inter-element delay amount τmaxT can be set. can. This means that it is possible to phase the delay time which is (N-1) times longer than that of the conventional receiving phaser which is limited by equation (2).

Further, the limit on the deflection angle θ is given by θ<sin ⁻¹ vT/d (5) and is determined by the sampling period T and the element spacing d, regardless of the number N of elements. Therefore, even if N is increased and transmission/reception is performed with a large aperture, a sufficiently large deflection angle can be obtained compared to the conventional one.

Figures 4a and 4b show a second embodiment of the invention.

14-2 to 14-N are sample and hold circuits,
C ₂ ' to C _N ' are control signals, and the others are the same as in FIG. 3a. FIG. 4b shows the control signals C ₁ to C _N and C ₂ ′ to
It is a diagram showing the timing of C _N ', where τ is the inter-element delay time for obtaining the deflection angle θ, and T is the sampling period.

Here, the received signals input to each element 1 to N are sample-and-hold circuits 10-1 and 14-2 to 1
4-N respectively control the control signals C ₁ and C ₂ ′~
It is held at the timing of C _N ′. The signals of elements 1 and 2 are added by an adder 13-2, and then sampled by a sample-hold circuit 10-2 at a time C 2 that is delayed from C ₂ ' by a settling time Δ of _14-2 . will be held. The added signals of elements 1 and 2 are added with the signal of element 3 in an adder 13-3, and then sampled and held by a sample-and-hold circuit 10-3 at a time C3 delayed by 2Δ from _{C3 '} . By repeating the same operation, the sample-and-hold circuit 10-N samples and holds the phased sum signal of the received signals from all the elements at the timing C _N , and outputs it to the output terminal 12-1.

In this embodiment, as in the first embodiment, the limit on the delay time τ between each element is given by equation (4). Therefore, regarding the deflection angle θ, the relationship is expressed by equation (5), and the same effects as in the first embodiment can be obtained.

In the above explanation, the reception deflection angle of the ultrasound beam is explained in terms of the direction of the main beam for convenience, but the present invention is also applicable to the case of phasing the reception of the array element in order to focus the ultrasound beam. It is clearly possible.

〔Effect of the invention〕

As described above, according to the present invention, the phasing delay of each array element is configured by a sample-hold circuit, and the output signals are sequentially added in series, thereby phasing a signal delayed longer than the sampling period. becomes possible. In addition, since the maximum delay time does not increase with the number of array elements, the trapezoidal field of view obtained by this phaser has a large aperture and a large deflection angle compared to conventional linear scan or sector scan. It is expected that it will greatly contribute to diagnosis.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a trapezoidal field of view, Fig. 2a is a diagram showing the configuration of a conventional receiving phaser, Fig. 2b is an explanatory diagram of its operation, and Fig. 3a is an illustration of an embodiment of the present invention. The figure shown,
3b, c and d are diagrams explaining the operation, FIG. 4a is a diagram showing another embodiment of the present invention, and FIG. 4b is a diagram explaining the operation.

Claims (1)

[Claims] 1. Ultrasonic tomography in which a tomographic image is obtained by deflecting an ultrasound beam by controlling the amplitude and phase of the transmitted or received signal of each element of N consecutively arranged transducer elements. In an ultrasonic reception phasing circuit used in the apparatus, a variable delay means comprising a sample and hold circuit for phasing a delay depending on the deflection angle of the ultrasonic beam, and a settling time of the variable delay means for correcting the settling time of the variable delay means. The variable delay means is connected to the first array element arranged first of the elements, and the variable delay means is connected to the nth (n=2, 3,
..., N)th array element is connected to the fixed minute delay means, and the output terminal of the fixed minute delay means is connected to one input terminal of the addition means having two input terminals. The output terminal of the adding means is connected to the variable delay means, and the other input terminal of the adding means is connected to the nth array element, and the other input terminal is connected to the output terminal of the variable delay means connected to the (n-1)th array element. The ultrasonic receiver is characterized in that the received signal delayed longer than the sampling period of the received signal in each element is phased by sequentially adding the outputs of the variable delay means of the connected elements in series. Wave phasing circuit. 2. The ultrasonic receiving phasing circuit according to claim 1, wherein the fixed minute delay means is any one of an analog LC delay line, a charge-coupled device, or a sample-and-hold circuit.