JPH0131152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an azimuth adaptive phased array sonar that can be applied to ultrasound imaging devices and the like.

In particular, the present invention relates to an azimuth adaptive phased array sonar that can suppress artifacts caused by acoustically significantly hard test objects.

[Prior Art] Ultrasonic imaging equipment that irradiates acoustic pulses onto a test object from an array probe and observes the echo signals detects the presence of a prominent object that generates a large echo signal on the test object. There is a phenomenon in which multiple false images occur at positions equidistant from each other but at different angles. This is thought to be due to the generation of signals with an integral multiple or fraction of the phase (or frequency) in the echo signal.In order to suppress this artifact, the received signal must be passed through a bandpass filter. It is known that it is effective to remove frequency components that cause artifacts.

[Problem that the invention seeks to solve]

However, when this bandpass filter is used regularly, received signals other than pseudo images are also subject to frequency band limitations, resulting in a disadvantage that the resolution of the image deteriorates overall. In particular, it has been difficult to identify small-sized test objects.

The purpose of the present invention is to eliminate the aforementioned drawbacks by suppressing artifacts caused by acoustically significantly hard test objects without affecting the sharpness of the images of other test objects. An object of the present invention is to provide an azimuth adaptive phased array sonar that improves image quality.

[Means for solving problems]

The present invention improves image quality by suppressing pseudo images caused by strong reverberants existing within a beam scanning range, and includes an array probe configured by arranging a large number of transducers; a transmitting/receiving device that obtains an image of the object by phase-driving the probe and scanning the transmitted and received ultrasonic beam in a fan shape; a cross point switch that inputs the received output signals of the plurality of vibrators, and a delay circuit with taps that receives signals from a large number of output terminals distributed by the cross point switch as tap inputs, respectively. In the azimuth angle adaptive phased array sonar, a filter whose pass band is variably controlled is provided in the path of the output signal of the delay circuit, and an echo signal exceeding a predetermined level is sent to the output signal of the delay circuit. a detection circuit for detecting this, and a control means for narrowing the pass band of the filter in the vicinity of the timing at which the echo signal is detected for the next and subsequent scans of the ultrasonic beam according to the output of the detection circuit. It is characterized by being prepared.

[Explanation of principle]

Hereinafter, the principle of the present invention will be explained in detail using the drawings.

FIG. 1 shows that when a sound ray 102 transmitted and received from an array probe 101 is reciprocated within the range of deflection angle θ, a strong echo body 103 existing in the trajectory of the sound ray 102 is generated. A state in which a false image occurs along a broken line 104 is shown.

A in FIG. 2 shows the echo signal amplitude in the time domain, and the symbol a in the figure shows the echo signal amplitude at the time when the sound ray 102 crosses the strong echo body 103 as shown in FIG. The symbol b in the figure indicates that the sound ray 102 is the strong reverberant 1 as shown in Figure 1.
03 is shown. The straight line c indicates the threshold value set for the echo signal amplitude, and the straight line d
indicates the lowest detection level.

The echo signal indicated by the symbol a has an amplitude exceeding the threshold value indicated by the straight line c at the position of the strong echo body.

〔Example〕

The present invention will be explained in detail below using the drawings.

FIG. 3 is a block configuration diagram showing the configuration of the main parts of the apparatus according to the embodiment of the present invention. In FIG. 3, a trigger generated from a trigger generator 1 whose timing is controlled by a controller 12 is applied to a transmission delay map circuit 2a. In the delay map circuit 2a, the same number of delay lines as the transducers 4 are prepared, and each delay line is
The line delay amount is controlled by the controller 12, and the delay time distribution is determined so that the beam deflection angle is a predetermined angle, taking into account beam focusing and the like. The delay output obtained through such a delay map circuit 2a is sent to the pulser 3.
given to. The pulsers 3 are individually directly connected to the simultaneously energized transducers 4, and are energized by the output of the delay line corresponding to each pulser 3 to generate transducer drive pulses and drive each transducer. Excite user 4. As a result, an ultrasonic beam is projected from the array transducer 4 in a determined direction.

After that, each echo signal received by each element of the transducer 4 and converted into an electric signal is amplified by a predetermined amplification factor in the receiving amplifier 5, and
Next, the synchronism of each echo signal is corrected through the reception delay map circuit 2b, which is set to have the same delay time distribution as the transmission delay map circuit 2a, and the echo signals are combined into a single signal. is led to circuit 7. The signal processed by the signal processing circuit 7 is connected to a video signal output terminal 13.

The feature of the present invention is that the filter 6 is constituted by a variable filter whose passband is variable. Furthermore, a circuit for controlling this filter 6 is added. That is, the output of the signal processing circuit 7 is branched and applied to one input of the comparison circuit 8. The other input of this comparison circuit 8 is connected to a threshold generator 9 that provides a threshold value. The output of the comparison circuit 8 is applied to a convolution circuit 10, subjected to convolution processing, and then applied to a parameter control circuit 11. The output of the parameter control circuit 11 is configured to individually control variable elements (for example, variable quantity elements) of the filter 6 to change their frequency characteristics.

The operation of this circuit will be explained with reference to FIG. 2. The output of the signal processing circuit 7 is branched, and the video signal corresponding to the echo signals a and b in FIG. On the other hand, the threshold value generator 9 sets a threshold value corresponding to the value shown in c of FIG. If the comparator circuit 8 determines that there is a video signal exceeding the threshold, it outputs a signal corresponding to B in FIG. This signal is applied to a convolution circuit 10, and the output of this circuit has a waveform whose rising and falling portions are more gently sloped in a curved shape, as shown in FIG. 2C, compared to FIG. 2D. This waveform signal is applied to the parameter control circuit 11. With this gradual change waveform, parameter changes are not made suddenly, and therefore image changes are made slowly, resulting in an effect that does not give rise to unnaturalness due to pseudo-image suppression.

The output of the parameter control circuit 11 is given to the variable filter 6, and the passband width of the filter 6 is changed for the next scanning by the sound ray for a time Tx that is slightly longer than the time it takes for the sound wave to pass through the strong reverberant. Control is performed to narrow it down. With this control, the filter 6 removes the strong reverberation signal caused by the strong echo body in the next scan and subsequent scans, so that the pseudo image caused by the strong echo body is removed.

Furthermore, when the sound ray passes through the strong reverberant, the parameters of the filter are restored to their original states, and a video signal that provides a normal clear image is applied to the terminal 13.

〔Effect of the invention〕

In the circuit of the present invention, the passband of the bandpass filter is automatically narrowed near the timing when a strong reverberation signal from a strong reverberant is received. This has the effect of suppressing the appearance of false images caused by strong reverberants present in the area.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a situation in which a false image occurs when a strong reverberant exists within the ultrasound beam scanning range. FIG. 2 is a diagram showing the relationship between echo signal amplitude and bandwidth limit signal generation. FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention. 1...Trigger generator, 2a, 2b...Delay map circuit, 3...Pulser, 4...Array
Transducer, 5... Receiving amplifier, 6... Variable filter, 7... Signal processing circuit, 8... Comparison circuit, 9... Threshold generator, 10... Convolution circuit, 11... Parameter. Control circuit, 12... Controller, 13... Video signal output terminal, 101... Array probe, 102...
Sound ray, 103...Strong reverberant, 104...Pseudoimage generation part.

Claims (1)

[Claims] 1. An array probe configured by arranging a large number of transducers, and an ultrasonic beam that is transmitted and received by driving the phase of this probe to scan a target object in a fan shape. a transmitting/receiving device for obtaining an image; the receiving section of the transmitting/receiving device includes: a cross point switch for inputting received output signals of the plurality of transducers coming from the array probe; - In an azimuth angle adaptive phased array sonar equipped with a tapped delay circuit which is distributed by a switch and receives signals from a large number of output terminals as tap inputs, the passband is variable in the path of the output signal of the delay circuit. a filter to be controlled; a detection circuit for detecting that an echo signal exceeding a predetermined level is sent to the output signal of the delay circuit; and a detection circuit for determining subsequent scanning of the ultrasound beam in accordance with the output of the detection circuit. An azimuth angle adaptive phased array sonar comprising: control means for narrowing the passband of the filter near the timing at which the echo signal is detected.