JPH0123751B2 - - Google Patents

Description

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

[Prior art]

Conventionally, an array probe consisting of multiple transducers (hereinafter referred to as elements) is used, which is phase-driven to perform sector scanning and transmit and receive ultrasonic waves in a desired range. Phased array sonar is well known.

By the way, in a phased array sonar, as the azimuth angle θ (the deflection angle of the ultrasonic beam from the central axis of the probe) increases, the gain decreases extremely. The reasons for this are that the aperture of the probe appears oblique and the actual aperture size decreases, that the directivity of each element worsens as the azimuth angle θ increases, and that it is attached to the front of the array probe. This is due to the presence of aberrations in the acoustic system, including the lenses and matching layers used in the process.

Therefore, as the azimuth angle θ increases, the gain on the receiver side has to be increased, but the signal quality still deteriorates (deterioration of S/N, artifact, resolution, dynamic range, etc.). It cannot be avoided.

[Purpose of the invention]

An object of the present invention is to provide an azimuth-adaptive phased array that can prevent the deterioration of image quality that occurs with the azimuth angle θ as described above, and can extract and display as much useful information as possible.・The purpose is to provide sonar.

[Summary of the invention]

In order to achieve this purpose, the present invention increases the gain on the receiver side in response to an increase in the azimuth angle, and also increases the rejexion level in response to an increase in the azimuth angle. It is characterized by

〔Example〕

The present invention will be explained in detail below using the drawings. The array probe 1 is composed of 64 elements and is connected to the transmitter/receiver/beam deflector 2. The transmission/reception/beam deflection unit 2 drives the array probe 1 based on the scan control signal from the scan control data generation unit 3.
The configuration is such that the echo signal detected at this time is sent to the next stage. The echo signal reception processing line includes a logarithmic amplifier 4 that amplifies the output of the transmitter/receiver/beam deflector 2, a detector 5, and a variable gain amplifier 6.
, a variable filter 7, and an output stage amplifier 8 are connected in series. The output of the output stage amplifier 8 is given to the CRT 9. The sound ray number determination section 10 determines the sound ray number based on the clock signal (transmission/reception trigger), and outputs the sound ray number signal to the scanning control data generation section 3 and the reception control data generation section 11.
The reception control data generating section 11 outputs a control signal determined in relation to the sound ray number to the variable gain amplifier 6, the variable filter 7, and the deflection control section 12, respectively. At this time, only the bias signal (rejection level control signal) to the variable gain amplifier 6 is converted into an analog signal via the D/A converter 13. The deflection control section 12 outputs a deflection signal based on the sound ray number to each of the X and Y deflection circuits 14 and 15 while keeping timing according to a clock signal. The deflection signals of the X and Y deflection circuits 14 and 15 are sent to the X deflection coil and Y deflection coil of the CRT 9.
given to each deflection coil.

In the above configuration, the input/output characteristics of the variable gain amplifier 6, that is, the gain and relocation level, are determined by the gain control signal and bias signal output from the reception control data generation section 11 according to the azimuth (acoustic ray number). determined by. Figure 1 shows its characteristics. Now, the decrease in sensitivity of the array probe to the azimuth angle |θ| is as shown by the curve in Figure 1A. Therefore, in order to compensate for this decrease in sensitivity, the gain of the variable gain amplifier 6 is increased as the azimuth angle |θ| increases like a curve. At the same time, the rejiexion level is changed to match the noise floor raised by the increase in gain, as shown in FIG. It is preferable that the difference between the gain and the rejexion level is always approximately constant with respect to |θ|.

In this way, if the received signal from the array probe is received and processed on the receiver side while changing the gain in relation to the azimuth, and also rejiggering at a level that changes in relation to the azimuth, the azimuth It is possible to collect more useful information even for objects where θ is large, and a high-quality display image with less noise is guaranteed.

On the other hand, in CRT displays, etc., the relationship between the received signal (echo signal) processed as described above and the brightness level of the display (processing curve or γ
The characteristic) may be changed in relation to the azimuth angle θ as shown in FIG. That is, the contrast may be maintained by increasing the gradient and the intersection with the echo level axis according to |θ|.

Note that the intersection points l ₁ and l ₂ with the echo level axis in this case correspond to the resiexion level.

Furthermore, the γ correction curve may also be changed depending on |θ|.

Further, when the γ characteristic is changed as described above, the gradient becomes steep in the portion where |θ| is large, so the contrast is too strong and the screen becomes glare and difficult to see. In order to prevent this, it is desirable to perform smoothing using a circuit configuration as shown in FIG. 3, for example. In FIG. 3, the echo signal that has been subjected to the above-mentioned signal processing is once passed through a variable low-pass filter 31, and then the CRT
The signal is input to the video amplifier 32 for the 33 drive.
The variable low-pass filter 31 has its frequency characteristics changed as shown in FIG. 4 by a control voltage related to |θ| (given from a controller (not shown) installed in the receiver, etc.). , |θ| increases, video signal smoothing is strengthened, and screen glare is suppressed.

〔Effect of the invention〕

As described above, according to the present invention, by appropriately adjusting the gain and rejudgement level on the receiver side according to the azimuth, it is possible to prevent image quality from deteriorating due to the azimuth.

Further, by changing the γ characteristic or the γ correction curve depending on the azimuth angle, it is possible to maintain the contrast of the image in a desired state.

Further, when smoothing processing is applied, excessively strong contrast is automatically weakened, making it possible to obtain an image that is easy to see.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the principle of the present invention, Fig. 2 is a diagram showing γ characteristics, Fig. 3 is a diagram showing the main part configuration when performing smoothing processing, and Fig. 4 is a diagram showing the characteristics of the variable low-pass filter. FIG. 5, which is a diagram for explanation, is a configuration diagram showing an embodiment of the present invention. 31...Variable low-pass filter, 32...Video amplifier.

Claims (1)

[Claims] 1. In a phased array sonar that uses an array probe formed by arranging a plurality of transducers and performs sector scanning by moving and driving the array probe, the sound ray in sector scanning is The echo signal from the array probe is received and processed while changing the gain and rejudgement level in the receiver in accordance with the azimuth, using a control signal created corresponding to the number. An azimuth angle adaptive phased array sonar characterized in that the azimuth angle adaptive phased array sonar is configured to display an image of an echo signal obtained by adjusting the azimuth angle. 2. The azimuth angle adaptive phased array sonar according to claim 1, wherein the gain and redirection level are increased as the azimuth angle increases. 3. The azimuth angle adaptive phased array sonar according to claim 1, wherein the relationship between the echo level and the display brightness level is changed depending on the azimuth angle when displaying the image. 4. The azimuth angle adaptive phased filter according to claim 3, characterized in that the smoothing applied to the echo signal for image display is enhanced according to the azimuth angle to suppress excessive contrast. array sonar.