JPS62268537A - Ultrasonic reciving phasing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the configuration of an ultrasound receiving phasing circuit in an electronic scanning ultrasound diagnostic apparatus.

[Conventional technology]

Various electronic scanning ultrasound diagnostic devices have been proposed that use array transducers to send and receive focused ultrasound beams while sequentially switching the beam direction or position, and display the detected intensity of reflected sound waves on a scanning screen. .

In this system, the focal length of the receiving beam is changed over time so that all of the reflected sound waves that are clearly detected over time after one concave transmission are focused, and the focal length of the receiving beam is changed over time so that it is high at all depths within the display area. There is a device called a reception dynamic focus method that attempts to obtain high-resolution images. To realize this method, it is necessary to switch the receiving focus at high speed, and it is necessary to use a receiving phaser to quickly switch the tap of the delay line for each of the multiple transducer elements used for receiving waves. be. This tap switching causes noise, so
The device disclosed in JP-A-56-112234 is equipped with two sets of receiving phasers, and for ultrasonic beams in the same direction,
When one phaser is used, move the receiving focus by switching taps on the other phaser.

[Problem that the invention seeks to solve]

The purpose of the device disclosed in the above-mentioned publication is to perform phasing in the other phaser during the period when noise is generated due to the tap switching of the individual delay circuits of the -set of phaser. This method attempts to prevent noise from being mixed in by alternately using phasers to continuously switch the reception focal length. However, since the delay time after switching also differs depending on the delay circuit connected to each vibrator, the noise in the phased and summed signal will continue for a long time due to the difference in delay time. Therefore, during the duration of this noise, it is necessary to perform phasing with the other phasing device, and therefore the number of alternating switchings, that is, the number of focal points cannot be made sufficiently large.

To explain using FIG. 5, #1 to #1 of the vibrator array 23
Wave reception is performed using element #4, and one phaser is used to convert the wavefront from F1 (solid line in Figure 5 (a)) to the wavefront from F3 (
In order to switch the focal point to the dotted line in FIG. 5(a), it is assumed that tap switching of the elongated circuit for each element is performed at time T1 in the figure. The received signal of each element is 1. The switching noise continues for a period of time (typically about 5 μs). However, after T1, a delay must be given to the receiving side of each element so that the receiving side of the wavefront from F a is in phase, so as shown in Fig. 5 (
Noise continues in the phasing addition output of the phasing device shown in c) for a time equal to tn plus the maximum time difference (τ) of phasing delays of each received signal. Therefore, during the period (10τ), the second phaser performs phasing on the wavefront from the focal pressure RFZ. So, generally 5 to 101. L5 or more may be -1; within the switching noise generation time (10 to 15 μs)
Since the focal point cannot be switched using the second phaser, it is difficult to provide a sufficiently large number of focal points and obtain a high-resolution image.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to shorten the duration of noise caused by the gradual switching of each of a plurality of receiving phasers that are used alternately for continuous switching of receiving focal points, thereby achieving high-speed and multi-stage focusing. It is an object of the present invention to provide an ultrasonic receiving phasing circuit that enables distance switching without introducing noise and obtains a high-resolution image.

[Means for Solving the Problems] In the present invention, for each variable delay means that gives a delay according to the wave front to each received signal of a plurality of elements, a It is characterized by a configuration in which tap switching is performed based on timing differences.

[Effect]

According to the above configuration, in the output after being delayed by each variable delay means, /l noise due to tap switching continues within the same period, and the outputs are added together to obtain the output. At the phase outputs, the duration of the noise due to tap switching is approximately equal to the duration of the noise of the individual variable delay circuits. Therefore, when the above configuration is employed in a device that sequentially changes the focus by alternately using a plurality of reception phaser, the cycle of alternate switching can be shortened and the number of stages of focus switching can be increased.

〔Example〕

The present invention will be explained in detail below using FIG.

FIG. 1 is a diagram showing the focus switching method of the present invention. 1st
When switching the focus of the received wave from the focus F1 to the focus F3 shown in Figure (a), each element 41 corresponding to the wavefront F3 from F3
The phasing delay time of each received signal of ~#4 is set to τ2. (
i is the focal point number and j is the receiving element number. ). However, the element number that receives the latest signal among the same wavefront is j=
1 and τl J = O.

At this time, the tap switching time φ4 for switching the delay amount of each received signal shown in FIG. 1(b) is T
14 Change it as soon as possible. Therefore, since the taps of each delay circuit are switched at a time synchronized with the wavefront to be phased after switching, switching noise mixed into the output of each delay circuit connected to each receiving element will all appear at the same time. .

Therefore, the duration of the switching noise in the phasing and summation output is calculated as the switching noise time of one delay circuit 1++ (approximately 5μ
s).

FIG. 2 shows the main parts of an embodiment of the invention. Delay circuit 21 for wave transmission. Driver 22. Amplifier for wave reception 24. First variable delay circuit 25. The second variable delay circuit 26 is provided for each element of the array probe 23 that is used simultaneously. Therefore, it should be understood that they are provided multiplexed in the direction perpendicular to the plane of the paper, and an adder is provided at point 27 for adding up the respective outputs of the first variable delay circuits 25 provided in the multiplexed manner. The variable delay circuit group and the adder form a first phaser. Similarly, at point 28, a second variable delay circuit 26 is provided in multiple directions perpendicular to the plane of the paper.
An adder is provided to add the outputs of the second
A phaser is formed.

1st. The output of the second phasing device is alternately selected by the switch 29.6 The output of the selected phasing device is subjected to processing such as logarithmic compression 9 and gain adjustment according to the depth of the reflected wave in an image processing circuit. Display it on the screen of the display 31.

Figure 3 shows the operation of each part of Figure 2, and (a) shows a wave transmission trigger that is applied periodically. The signal is given by the delay circuit 21 and amplified by the driver 22 to drive each element of the probe 23 in a pulsed manner. The reflected wave generated by the transmitted wave is detected by each element, and the received signal is sent to the first . It is applied to the second variable delay circuit 25,26. Each variable delay circuit has a tap switcher 35.3 for switching the amount of delay.
6, and for each element, the tray delay specified by the focus switching control signal 37, 38 is performed depending on the wave front from the reception focal length. The outputs of the variable delay circuits for each element are added by the adder provided at 27 or 28 as described above, thereby phasing the received signal according to the focal length. The outputs of the first phaser (the adder in the variable delay circuits 25 and 27 of each element) and the second phaser (the adder in the variable delay circuits 26 and 28 of each element) are shown in FIG. They are alternately selected by the switch 29 as shown in b). During the period when the second phaser is selected, the first phaser changes the focal length to Ft and Fa as shown by the solid line in FIG. 3(c).

Switch to FTh. That is, the tap changer 35 of the variable delay element for each element is switched so that the received signals from each element are in phase with respect to the wavefront from each focal length. In the second phaser, the focal length is switched between F2, F4, and Fe during the period when the first phaser is selected, as shown in FIG. 3(d), so that the output of the switch 29 is As shown in FIG. 3(d), a received signal is obtained in which the focus is sequentially switched from Fl to FB. In this embodiment, the switching timing of the tap changers 35 and 36 for each variable delay circuit extending the signal of each element is determined as shown by dotted lines in FIGS. 3(C) and 3(d). to be different. That is, as described in FIG. The tap changer 35 of the delay circuit 25 is switched at different timings as shown by the dotted line, thereby changing the focus F3.
Within the period in which a signal phase-aligned with the wavefront from
Noise caused by switching in the output of multiple variable delay circuits that delay the received signal for each element appears during the same period. Focus switching from F3 to F8, and second
The same is true for switching the focus from F2 to F4 and from F4 to FB in the phaser, and the dotted line indicates the switching timing of the tap changer of the variable delay circuit for each element corresponding to the wavefront from the focus after switching. Make the difference as shown in . As a result, focus switching was performed at the timing of the solid lines in FIG. 3(c) and (d) for the first phasing ratio (and the phasing output of the second phasing device), and the element The switching noise duration time will not be extended due to the difference in delay amount.

The first one like this. When the reception is completed by alternately selecting the second reception phaser, the direction of transmission and reception is changed 8 times, and the first and second reception phasers are changed in the same manner. The second receiving phaser 7'i selects and receives the signal. Therefore, the first. In the second phaser, each focus is switched from the focus F 6 r Fe to the focus of the next received wave after transmission. Regarding the tap switching of each variable delay circuit for this focus +2J switching, the timing may be adjusted depending on the amount of delay after switching, but in this example, from one wave transmission to the next wave transmission. Because there is plenty of time for
For information on switching the focus of receiving waves between transmitting waves, see Section 1. The taps are switched all at once by the second receiving phaser.

FIG. 4 shows a focus switching control signal 37 or 38 that controls the switching of the tap changer 25 or 26 in order to perform tap switching at a timing corresponding to the delay amount after switching the signal of each element as described above. It explains the occurrence,
FIG. 4(a) shows the circuit configuration, and FIG. 4(b) shows the timing of each part. After the ultrasonic pulse transmitted at the rising time of the Re5et pulse is reflected in the living body, Received by each receiving element. Therefore, the signal received by the j-th element is T s
The section J is delayed in phasing so that it converges at F3.

The relationship between the focus fixing section T I J and the phasing delay time is given by the following equation.

T I J = T low τIJ + τI-2, j° = (]
) However, Tll is the focus fixing section of the element that receives the signal most late.

T, J, and TIJ are stored in the read-only memory 41, and the time of T I J is counted by the TIJ counter 42, and by the ripple carry output signal φ,
At the same time as the memory address counter 43 is advanced, the next data TI+z, J, τl+2 . J are latched into latch circuits 44 and 45, respectively. Therefore, tap switching'd:! , 35 is 1 for each TIJ. An input tap to the C delay line is selected, so that the jth received signal is delayed by the selected tap.

By providing the control circuit 1-j shown in FIG. 4(a) for each variable delay circuit provided for each receiving element,
The phasing delay time can be switched at time φ synchronized with the received wavefront.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to shorten the time during which switching noise occurs during phased output, which occurs due to tap switching of a variable delay circuit for focus switching. Therefore, the number of focus switching stages can be increased, and high-resolution images can therefore be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the timing of focus switching in the present invention, FIG. 2 is a diagram showing the circuit structure of the main part of the embodiment of the present invention, and FIG. 3 is a diagram showing the timing of each part in FIG. 2. , FIG. 4 is a diagram showing a control circuit used in the embodiment of FIG. 3 and its operation, and FIG. 5 is a diagram showing an embodiment of a conventional point switching control circuit. 23... Probe, 2!5, 26... Variable delay circuit, 3
5゜3 days...Tap changer, 37.38...Focus switching control signal.

Claims (1)

[Claims] 1. An ultrasound diagnostic apparatus that focuses or deflects an ultrasound beam to obtain a tomographic image by controlling the phase of transmitted and received signals of a plurality of piezoelectric elements, including a plurality of phasing means and a focal point. A first switching means for switching, and a control means for controlling each switching time so that switching noise of the first switching means generated in each received signal is output at the same time after phasing. An ultrasonic receiving phasing circuit comprising: 2. The apparatus according to claim 1, wherein the ultrasonic receiving phasing circuit comprises a second switching means for switching the phasing outputs of the plurality of phasing means.