JPH0136152Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an azimuth angle adaptive phased array sonar that is applied to ultrasonic imaging devices and the like.

Conventionally, an array probe consisting of multiple transducers (hereinafter referred to as elements) has been used, and by driving the array in phase, the transmitted and received ultrasonic beams are swung in a fan shape (Figure 1). Such sector scanning phased array sonar is well known.

However, in conventional phased array sonar of this type, the aperture of the linear array probe appears diagonally as the deflection angle θ, or azimuth angle, of the ultrasonic beam deviates from 0° (front direction), so the effective In addition to the simple problem of poor dimensions and reduced sensitivity, various problems arise.

First, unless the gain when amplifying the echo signal is corrected by an even function of the deflection angle θ, shading will be noticeable and it will not be practical.

Gain correction basically only needs to compensate for the phenomenon that the aperture appears oblique (the effective aperture _APS becomes narrower), so the echo signal is logarithmically compressed and then the detected video signal is added with its inverse component. In other words, it is sufficient to add components equivalent to 2log ₁₀ cosθ. However, this is not the only phenomenon; there is also a component of decreased sensitivity to azimuth angles of individual elements. Typically, at an azimuth angle of 45 degrees, there is a drop of about 6 to 9 dB during the round trip of transmission and reception, and this cannot be ignored.

The purpose of this invention is to focus on these points, compensate for the essential decline in imaging ability that occurs due to azimuth angle, and create a uniform and good image that does not feel strange to the naked eye, regardless of the azimuth angle θ. The purpose of this project is to realize an azimuth-adaptive phased array sonar that provides the following characteristics.

The present invention will be explained in detail below using the drawings. FIG. 2 is a diagram showing an embodiment of the present invention, in which a correction function generator 20
The configuration is the same as that of a normal conventional phased array sonar except for this part.

First, the configuration of a part comparable to a conventional sonar part will be explained. A trigger pulse is generated by the trigger generator 1 at a predetermined timing under the control of the controller 7. This trigger is output after being delayed for a predetermined time via a transmission delay map _2a (consisting of a plurality of delay lines) that provides the time delay distribution necessary to phase drive the array transducer 4, A pulsar group 3 consisting of a plurality of pulsers 3 ₁ to 3 _o configured to individually energize each element of the transducer 4 is energized. This allows transducer 4
An ultrasonic beam is projected from the target object, and the subsequent reflected wave from the object is received by the transducer 4 and converted into an electrical signal, which is appropriately amplified via the amplifier 5 and then guided to the reception delay map _2b . . The delay map _2b has the same configuration as the transmission delay map _2a and has a similar delay time distribution, and the simultaneity of each echo signal is corrected and combined into one echo signal. The combined output extracts only the echo signal in the desired frequency band through a bandpass filter (variable is also available), is appropriately logarithmically compressed and detected in the logarithmic compression/detection circuit 8, and is then output at the input stage of the lowpass filter 9. After adding it to the output of a correction function generator 20, which will be described later, high frequency components are removed.
The signal is sent out as a video signal via the video amplifier 10.

In the correction function generator 20, reference numeral 21 is a RAM buffer memory, in which a central processing unit (CPU) 30 indexes a correction data table that does not calculate a correction function according to the probe used and writes it into this RAM buffer memory, and thereafter during scanning. Data at a predetermined address (designated by the output of the scan address generator 22 that operates in conjunction with the timing of the trigger generator 1) is read out according to the azimuth angle θ given by the controller 7. . The read data (correction function value) is converted into an analog signal by the DA converter 23, then high frequency components are removed by the low pass filter 24, and then input to the low pass filter 9 of the receiving system.

The correction function written in the RAM buffer memory 21 is a correction amount that is a combination of 2log ₁₀ cosθ, which compensates for the reduction in effective aperture depending on the azimuth angle θ, and compensation for the reduction in sensitivity of each element to the azimuth angle, as described above. is expressed as a function of θ.

Note that this correction amount is not limited to being added to the output of the logarithmic compression/detection circuit at the input stage of the low-pass filter 9 as in the embodiment, but may be added to the received echo signal in the video amplifier 10.

According to such a configuration, for each reception period,
The correction function generator 20 operates, and the correction amount is added to the received echo signal for each azimuth in real time. Thereby, it is possible to obtain a video signal that is compensated for the decrease in sensitivity depending on the azimuth angle as described above.

Note that it is necessary to set an upper limit to the above-mentioned correction amount so that a larger correction amount is not output. In other words, if the correction (bias amount) is too much, other parts of the image will turn gray even when there is no echo or only noise.
This is because the screen becomes difficult to view, and it is necessary to set a limit on such bias (setting a so-called far gain).

Such a limit is from CPU30 to memory2
It may be applied at the stage of data provided to 1.

FIG. 3 is a block diagram of main parts showing another embodiment of the present invention. In the case of FIG. 2, the gain was corrected, whereas in the case of FIG. 3, the reduction in sensitivity is compensated for by increasing the transmission power. For this reason, the power supply voltage serving as the power of the pulser 3 is controlled in accordance with the azimuth angle θ, and as θ increases, the power supply voltage is also increased. Since the degree of enhancement is linear, it is sufficient to increase it by 1/cos ² θ in order to obtain a corrected form after the round trip of transmission and reception.
Therefore, the CPU 30 generates a function value of 1/cos ² θ according to the azimuth angle θ every time a scan is executed, and the DA converter 3 generates a function value of 1/cos 2 θ.
1 and converted into an analog signal, and this voltage makes the output voltage of the high voltage regulator 32 proportional to 1/cos ² θ. Figure 4 shows the azimuth angle θ (+45° to -45°)
This shows the change in the function 1/cos ² θ for .

In another embodiment of the present invention, the aperture may be made variable and controlled to be 1/cosθ times the aperture depending on the azimuth.

As explained above, according to the present invention, it is possible to automatically compensate for the decline in imaging ability caused by the azimuth angle, and to obtain a uniform and good image regardless of the azimuth angle θ, which does not feel strange to the naked eye. A phased array sonar can be realized.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the azimuth angle and the effective aperture, Fig. 2 is a diagram showing the main part configuration of an embodiment of the azimuth angle adaptive phased array sonar according to the present invention, and Fig. 3 is a diagram showing the configuration of the main parts of the azimuth angle adaptive phased array sonar according to the present invention. It is another Example figure. DESCRIPTION OF SYMBOLS 1...Trigger generator, _2a , _2b ...Delay map, 3...Pulser, 4...Array transducer, 6...Variable bandpass filter, 7...
... Controller, 8 ... Logarithmic compression/detection circuit, 9
...Low pass filter, 10...Video amplifier,
20... Correction function generator, 21... RAM buffer memory, 30... Central processing unit, 31... DA
Converter, 32...High pressure regulator.

Claims (1)

[Claims for Utility Model Registration] (1) In a phased array sonar configured to logarithmically compress and detect an echo signal obtained from a phased array probe to obtain a video signal, during sector scanning. The effective aperture area that changes depending on the azimuth angle θ and the azimuth angle θ
means for determining the amount of correction for each effective sensitivity that decreases in accordance with An azimuth angle adaptive phased array sonar characterized by comprising means for controlling the gain of a processing system or a transmission power system, and suppressing azimuth angle dependent shading. (2) The means for determining the correction amount is configured to output a compensation amount for the effective aperture area by 2log ₁₀ cos θ and a compensation amount for sensitivity reduction of each element with respect to the azimuth angle θ, in correspondence with the azimuth angle, The azimuth adaptive phased video signal generator according to claim 1, wherein the control means is configured to add the output correction amount to the logarithmically compressed and detected video signal. array sonar. (3) The means for determining the correction amount is configured to output a signal that changes at 1/cos ² θ in response to the azimuth θ, and the control means controls the phased array probe based on the signal. The azimuth adaptive phased array sonar according to claim 1, characterized in that the azimuthal adaptive phased array sonar is configured to control the power of the pulsar that energizes the sonar. (4) The means for determining the correction amount is configured to output a signal that changes the width of the aperture of the phased array probe in proportion to 1/cosθ in response to the azimuth angle θ. An azimuth angle adaptive phased array sonar according to claim 1 of the utility model registration claim. (5) The azimuth adaptive phased sensor according to claim 2, wherein the means for determining the correction amount is configured such that a far gain limit is applied to the correction amount. array sonar.