JPS60382A - Azimuth angle adaptive type phased array sonar - Google Patents

Abstract

PURPOSE:To improve picture quality and to extract and display effective information precisely by increasing the gain of the receiver side in accordance with the increment of an azimuth angle and increasing a rejection level in accordance with the increment of the azimuth angle. CONSTITUTION:The gain of the receiver side is increased in accordance with the increment of an azimuth angle so as to compensate the reduction of sensitivity of an array probe to the azimuth angle. Simultaneously, a rejection level corresponding to a noise flower increased by the increment of the gain is changed. It is preferable to keep the difference between the gain and the rejection level always constant to the azimuth angle. In addition, a gamma correcting curve may be changed in accordance with the azimuth angle. In this case, a signal is smoothed by a variable low pass filter 31 in accordance with the azimuth angle to reduce glittering on a screen.

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, a phased array probe uses an array probe consisting of multiple transducers (hereinafter referred to as elements), and performs full sector scanning by driving the probe in phase, transmitting and receiving ultrasonic waves in a desired range.・Nuna is well known.

By the way, in phased array sonar,
When 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 This is because there are aberrations in the acoustic system, including the lenses and matching layers used.

Therefore, as the azimuth angle θ increases, the gain on the receiver side has to be increased, but the signal quality still deteriorates (
S, artifact, resolution.

deterioration of dynamic range, etc.) 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 that can extract and display as much useful information as possible.・The aim is to provide the following.

[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 rejection level in response to an increase in the azimuth angle. Features and features.

〔Example〕

The present invention will be described in detail below using the drawings. The decrease in sensitivity of the array probe with respect to the azimuth angle 1θ1 is as shown by the curve ■ in Figure 1 (a).Therefore, in order to compensate for this decrease in sensitivity, the gain on the receiver side is adjusted according to the azimuth angle as shown in the curve ■. 1θ1
It increases as the number increases. At the same time, the rejection level is changed as shown in FIG. The difference between gain and injection level is always vcf for lθ1
'! , is preferably constant.

If the reception signal from the rejection array probe is processed on the receiver side while changing the gain in relation to the azimuth, and at a level that also changes in relation to the azimuth, It is possible to collect more useful information even for objects in areas where the azimuth angle 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 luminance level of the display (processing curve or γ characteristic) changes in relation to the azimuth θ, as shown in Figure 2. It may also be configured to do so. That is, the contrast may be fully maintained by increasing the gradient and the intersection with the echo level axis according to 1θIK.

Note that the intersection point t with the echo level axis in this case.

and t2 correspond to the rejection level.

Furthermore, the γ correction curve may also be changed according to 1θ1.

Further, when the γ characteristic is changed as described above, the gradient becomes steep in the portion where 1θ1 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 Figure 3, for example.
In FIG. 3, the echo signal that has been subjected to the above-described signal processing is once passed through the variable low-pass filter 31 and then transferred to the CRT 3.
3 drive video amplifier 32. The frequency characteristic of the variable low-pass filter 31 changes as shown in Figure 4, depending on the 1θIK-related control surface and pressure (given from a controller (not shown) installed in the receiver, etc.). As 1θ1 increases, the smoothing of the video signal is fully strengthened and screen glare is suppressed.

〔Effect of the invention〕

As described above, according to the present invention, by appropriately adjusting the gain and projection level on the receiving R aircraft side according to the azimuth, it is possible to prevent image quality from deteriorating due to the azimuth. Can be done.

Further, by changing the γ characteristic or the γ correction curve depending on the azimuth angle, the contrast of the image can be maintained in a desired state.

In addition, smoothing processing is applied, and in this case, too strong contrast is automatically weakened,
All images can be viewed easily.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention in detail, and FIG. 2 is a diagram for explaining the present invention in detail.
FIG. 3 is a diagram showing the main part when smoothing processing is performed, and FIG. 4 is a diagram illustrating the characteristics of the variable low-pass filter. 31...Variable low-pass filter 32...Video amplifier.

Claims (4)

[Claims] (1) In a phased array sonar that uses an array probe consisting of multiple transducers and performs sector scanning by moving the probe in phase S, the gain in the receiver is adjusted according to the azimuth angle. The azimuth adaptive phased sensor is configured to receive and process echo signals from an array probe while changing the rejection level and to display the processed echo signals as an image.
Alley nner. (2) The azimuth angle adaptive phased filter according to claim 1, wherein the gain and rejection level are increased as the azimuth increases.
array sonar. (3) The azimuth angle adaptive phased play mode according to claim 1, characterized in that when displaying the image, the relationship between the echo level and the display brightness level is changed according to the azimuth. Sonar. (4) Excessive contrast is suppressed by enhancing #J smoothing of the echo signal for image display according to the azimuth angle: azimuth according to claim 3, characterized by: Angle-adaptive phased array sonar.