KR870002046B1 - Imaging apparatus using ultrasonic waves - Google Patents

Abstract

The invention relates to a video signal processor that may be used for a ultrasonic diagnostic tester, non-destructive detector or underwater sonar of the sector-type employing steering and dynamic focusing. In the unit, an array transducer is connected to a steering delay circuit and then to the focusing circuit of the steering delay circuit to first perform steering to make delay for focusing. Thus, although steering circuits increase in number, focusing circuits are greatly reduced to result in a less total number of circuits for dynamic focusing, thus allowing more focusing points for better resolution.

Description

Ultrasonic Image Processing Device for Ultra Short Steering

1 is a schematic diagram showing a focusing apparatus of an ultrasonic image processing apparatus using a conventional array converter.

2 shows a received signal of an ultrasonic reflection signal.

3 is a two-dimensional cross-sectional view of an object for an ultrasound image signal.

4 shows a steering delay time.

5 is a diagram showing a steering delay time and a focusing delay time.

6 is a diagram showing a change in resolution in the case of dynamic focusing (two-point focusing).

7 is a schematic diagram of a steering delay circuit.

8 is a schematic diagram of a focus delay circuit.

9 is a system diagram of a dynamic focusing device at the time of reception by conventional focusing and steering.

10 is a system diagram of a dynamic focusing device at the time of reception by steering and focusing, showing an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic image processing apparatus, and more particularly, to an image processing apparatus of an ultrasonic imaging apparatus such as a medical diagnostic apparatus of a sector type, a non-destructive testing apparatus, and an underwater search apparatus by steering and dynamic focusing.

Ultrasonic image processing, as shown in Figs. 1 and 2, generates a pulse in a pulse generator, and the pulse signal is passed through the transmission side delay line and the mux circuit and is converted into N-waves. It is input to the individual transducers of an array transducer composed of transducer elements, and the electrical signals are converted into ultrasonic signals by the individual transducers. The ultrasonic signals travel through the object and reflect at one point within the object. After entering back into the converter, it is converted into an electrical signal at the converter, and after the mux and the delay line on the receiver side, the adder adds the converted signal from each converter and amplifies it. The amplified signal is then amplified. This process, which is converted into digital signal and then signal processed, is performed by changing the length and angle of the object to obtain a two-dimensional cross section of the object. As shown in the figure, it is displayed on the screen. Since the time when the ultrasonic signal is reflected from the object and returns is proportional to the distance, the coordinate axis of the image signal appearing on the screen has a length direction in the longitudinal direction.

Ultrasonic imaging devices composed of array converters are called " steering " so that the signals of the array's conversion elements are directed in the desired angle &thetas; direction by varying the time for applying an electrical signal to the conversion elements of each array as shown in FIG. Is done. The delay time ts of the required signal can be expressed as follows when the time required for the ultrasonic signal to proceed by the distance nd sin θ as shown in FIG.

(1)

(One)

Where C is the speed of the ultrasonic waves (about 1540 m / sec in water).

n is the array position order of the array

d is the array spacing

In addition, focusing is performed to increase the resolution of the object at an arbitrary angle. As shown in FIG. 5, in order to focus the ultrasonic signal at an arbitrary position R within the object, the time when the ultrasonic signal reaches R This should be the same. In other words, when the angle θ is zero, the signal must be delayed so that the signal from the point P in the object to the individual arrays has the same time when the signal arrives. At this time, the focusing delay time t _f is expressed as follows.

(2)

(2)

Where n is 1,2,3... N.

In ultrasonic image processing, ts and t _f are referred to as steering delay and focusing delay, respectively.

The method of steering and focusing the ultrasonic signal can be performed at the time of transmission or reception, and signal processing at the time of reception is more important because of the advantages of dynamic focusing. Dynamic focusing refers to a process of changing the focusing time t _f according to (2) according to the change of the length R in the object, and by the dynamic focusing, the resolution of the object can be kept almost independent of the length in the object. . 6 shows the case of two focal points.

However, it is difficult to increase the focusing point beyond a certain limit for real time image processing, and in general, focusing is more difficult to process than steering in a system that performs dynamic focusing.

In the conventional ultrasound imaging apparatus, since the processing method is simple, the method of separating and processing the steering and the focus is generally used in comparison with the method of simultaneously processing. In the former case, since the steering delay is linear, as can be seen in the equation (1) with respect to the array position order of the array, the steering delay is treated as a single delay circuit (commonly referred to as a summing delay line) as shown in FIG. Since it is possible to perform the focusing time delay, the steering delay is performed.

That is, as shown in FIG. 9, when the ultrasonic signal reflected at one point (focusing point) in the object is input to an array formed of N pieces (conversion device), each conversion device is converted into an electrical signal and the individual conversion devices are converted into individual signals. As shown in FIG. 8, a focusing circuit including an analog mux provided with a predetermined tab and a focusing delay line is connected to each other, and the analog delay line is changed by the analog mux to perform a focusing delay. Corresponding to the order n of the angle θ and the arrangement position of each conversion element among the taps of the steering delay circuit composed of a single delay circuit having a predetermined tap (much more than N) as shown in FIG. Signal processing of focusing and steering of the ultrasonic signal is completed by connecting to N taps so as to obtain a delay time expressed by Equation 1). In order to perform the dynamic focusing, as shown in Equation (2) above, the steering angle is changed each time the focusing point, that is, the length R, corresponds to the length R of the focusing point and the arrangement position sequence n of the array (converter). When θ is assumed to be zero, the taps of the focusing delay lines described above are switched to analog mux so that the delay of the signal is made such that the time to reach each array from the focusing point is the same. At this time, the number of taps of the analog delay line is given by the maximum delay time and the time quantitation value q. The delay time quantum value should be small enough so that the error occurring in the steering and focusing circuits is within tolerance. The number of taps T _N required for the delay circuit is approximately as follows.

T _{N =} T _fN + T _sN (3)

T _{fN =} N [Max (t _f ) / q] (4)

T _{sN =} Max (ts) / q (5)

Where T _fN and T _sN are the number of focusing and steering taps, Max (ts) and Max (t _f ) are the maximum delay times for focusing and steering, respectively, and N is the number of arrays.

As mentioned above, the focusing delay circuit of the prior art must be separate for each element, and when the dynamic focusing is performed, the analog mux circuit and the control circuit are as complicated as the analog delay element. The increase is enormous, which limits the number of focal points during dynamic focusing, resulting in very poor resolution.

Accordingly, an object of the present invention is to improve the resolution by increasing the number of focusing points by simplifying the circuit required by drastically reducing the connection delay circuit that is much more complicated than the steering processing circuit during dynamic focusing to solve the deficiencies of the prior art. . This object of the present invention can be achieved by performing a focusing process after performing a steering process when dynamically focusing an ultrasonic signal by the steering and focusing delay process.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, embodiment of this invention is described.

FIG. 10 illustrates an optimal implementation method according to the present invention, in which an ultrasonic signal input by reflecting at one point P in an object is converted into an electrical signal in an array ultrasonic converter composed of N arrays (converting elements), and then the N electrical The red signals are inputted into N / K = M steering delay circuits as a group according to the array sequence number of the array, and the steering signals are steered corresponding to the steering angle θ and the array array position number n, and are mutually symmetrical. Steering delay circuit pairs 1 and M (2 and M-1). An array of array converters, each of which is jointly inputted at the input terminals of the analog mux in the focusing circuit composed of M / 2, respectively, and is divided into the position of the focusing point P, that is, the length R and N / K = M. It is configured to perform a delay for the dynamic focusing by selecting a tap of the focusing delay line corresponding to the position. In other words, the steering delay circuit is focused on the array converter and the focusing circuit of the steering delay circuit is connected to perform the steering first (that is, after the first stage of steering), and then the delay for focusing is performed. Although the number of focusing circuits has increased, the number of circuits has been greatly reduced in the case of dynamic focusing.

The reduction of the number of circuits as a whole is described in detail below.

When the number of arrays (elements) for ultrasonic image processing is N, the number of arrays actually required for focusing is much smaller than N. In other words, the reason why N arrays are required is for steering. The difference is easily found in the above formulas (1) and (2). The maximum required steering delay time is several to tens of times larger than the maximum focusing time. For example, for medical diagnosis with R = 10cm, θ = 45 °, N = 64 and d = 0.3mm, substituting equations (1) and (2),

t _f = 1.3㎲, ts = 8.8㎲

It becomes Therefore, the ratio of steering and focusing time

γ = t _f / ts

In this case, the number of circuits M required for focusing is an integer greater than rN. As shown in FIG. 5, after the steering is performed first, it can be seen that the focusing time is halved because it is bilaterally symmetrical. In other words, the focusing circuit may be M / 2. Where the actual reduction ratio K is

K = M / 2 / N = M / 2N

Becomes Now, look at the increase in the complexity of the circuit caused by steering first. The above-described steering delay line of the prior art is configured as one delay circuit connected, but in the present invention, it is composed of several delay circuits as described above. If the order of each delay circuit is i, the maximum delay time per delay circuit is

I = 0,1,2... … M / 2-1,

to be. The sum of the steering delay time of the present invention,

If = M = / 2≫1

Ti = M / 8 Max (ts) = KN / 4 Max (ts) (7)

to be.

For example, when M = 16 and N = 64, the increase in equation (7) and the total steering delay time are doubled, but the decrease in the overall focusing delay time is eight times. Therefore, the number of taps of the delay circuit required in the present invention is

T ' _N = T' _FN + T ' _sN (8)

T ' _FN = M / 2 [Max (t _fN )] / q = KT _fN (9)

T ' _sN = M / 8 [Max (ts _N )] / q = M / 4NT _sN (10)

Becomes

As described above, in the device of the present invention, the number of steering delay circuits is increased, but the number of focusing delay circuits is further reduced, and the focusing of the ultrasonic signal tends to be dynamic focusing. Because of the enormous complexity of the device, the device according to the present invention is much simpler than in the prior art when the circuit for focusing and steering of the ultrasonic signal as a whole is viewed. Therefore, the focusing point can be increased at the time of dynamic focusing, so that the resolution becomes good.

In addition, when a sector-type ultrasonic imaging apparatus which performs ultra-short steering and a linear ultrasonic imaging apparatus which performs focusing only without steering, the focusing circuit is completely different in the prior art. In the present invention, since the ultrasonic signal after steering at the first stage is a signal compensated for the steering angle θ and the position change of the focusing point, the ultrasonic signal is compensated in correspondence with the position of the focusing point and the arrangement position of the array. Since the connection circuit to be connected is the same as the focusing circuit of the linear ultrasonic imaging apparatus which does not need to be steered, the sector type ultrasonic imaging apparatus and the linear ultrasonic imaging apparatus can be used in common with the focusing circuit.

Claims (1)

An image processing apparatus of an ultrasonic imaging apparatus for focusing an ultrasonic signal by a steering delay circuit and a focus delay circuit, comprising: an array ultrasonic wave comprising N arrays (converting elements) for converting an ultrasonic signal reflected from an object into an electrical signal A pair consisting of a N / K = M steering delay circuit which receives the transducers and the N electrical signals, each of which has K arrays as a group according to the arrangement order of the arrays, and a steering delay circuit having mutually symmetrical relations (1 And M), (2 and M-1)... … The signals steered at are added to select the analog mux in the M / 2 focusing circuits received at the input terminals and the focusing points in the object and the array positions of the array converter divided into N / K = M. Ultrasonic image processing apparatus comprising a tab of the focusing delay line to achieve the dynamic focusing of the inputted steered signals, the steering is performed first and then focused to simplify the focusing circuit.

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