JPH0148991B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a sonar wave transmission method that performs multi-beam forming, and more specifically, to a sonar wave transmission system that performs multi-beam forming. The present invention is devised, and therefore, aims to reduce variations in sensitivity or azimuth resolution between sound rays in simultaneous reception of multiple sound rays while utilizing the properties of a focused sound field.

(Prior Art) Conventionally, it has been widely known that reception multi-beamforming is performed in an attempt to increase the data rate in a pulse-echo type sound ray sequential imager. By the way, it is quite difficult to obtain sufficient azimuth resolution in imaging only by wavefront processing during reception, and it is necessary to prevent signals from arriving from unnecessary parts by focusing on transmitting waves, that is, "selective irradiation". It is essential for a good and beautiful picture. However, this is somewhat inconsistent with the idea of multi-beam reception. In particular, if the transmitting focus is too sharp, there will be too much of a difference between the main sound ray (the transmitting and receiving waves have the same focus and optical axis) and the secondary sound rays (the receiving focus and optical axis are slightly different from the transmitting wave). Therefore, essentially only the tonic line can be used.

For the purpose of preventing the above unnecessary components,
It is sufficient that the transmitted energy is confined approximately within a small region of interest (in terms of orientation).
In other words, it is sufficient to transmit waves with a slightly blurred focus.

In order to achieve such wave transmission, the aperture of the wave transmission may be narrowed, but this is not preferable because the power that can be output is small and the wave front becomes too diffused at a distance.

(Objective of the Invention) The present invention was made in view of the above points, and its purpose is not to narrow the transmitting aperture, but to devise a wavefront generation method to achieve a wide focal point and It is an object of the present invention to provide a multi-acoustic beam simultaneous reception sonar that employs a wave transmission method that can simultaneously obtain sufficient irradiation energy at a long distance.

(Structure of the Invention) The present invention achieves the above-mentioned object by using a pulse-echo type sonar that includes a single delay line for individually delaying pulses that individually drive multiple elements of a probe.
The probe includes a transmitting delay circuit and receiving delay circuits for the main sound line and sub-sound line each consisting of a large number of delay lines for respectively delaying the echo signals received by each element of the probe. , the delay map of the transmitting delay circuit is set so that the wavefront of the sound ray transmitted from the probe is approximately a bifocal wavefront, and the output of each of the receiving delay circuits is converted into one echo signal. The present invention is characterized in that received signals relating to a total of a plurality of acoustic scanning lines are simultaneously and independently extracted.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a polyphonic simultaneous reception sonar according to the method of the present invention. In the figure, 1 is a transmission trigger generator, 2 is a group of variable delay circuits that function as a transmission beamformer, and 3 is a group of pulsers (or power amplifiers) that drive each element of the array probe 4. The gist of the present invention can be implemented by the way the transmitting beamformer is set. The following array probe 4, first stage amplifier group 5, variable delay line group 6 (6a, 6b, 6
c), logarithmic amplifier 7 (7a, 7b, 7c), detector 8 (8a, 8b, 8c), video amplifier 9 (9a,
9b, 9c), A/D converter 10 (10a,
10b, 10c) and the image memory (also referred to as frame memory) 11 that retains display image contents, individually known general-purpose ones can be used. The means for reading and using the contents of the image memory 11 (displaying them or making a hard copy of them) is necessary for the system to achieve its intended effect, but is well known and will not be particularly explained. Here, from the receiving beamformer 6 to the A/D
Up to converter 10, 3 for tonic line and subtone line
Note that channels a, b, and c are provided. These are L shown in Figure 2 below.
It is designed to simultaneously receive M and R (left, main, and right) received sound rays, and it goes without saying that the delay maps with slightly different azimuths or beam center lines (optical axes) are used for each receiver. The wave beamformers 6a, 6b, and 6c are set.

As mentioned above, the gist of the present invention is to receive echoes for all of these L, M, and R sound rays from a substantially equal position.
The delay map of the delay circuit 2 forming the transmission beamformer is set so that the beam transmitted and received from the probe 3 has wavefronts 31a and 31b (showing the wavefront just before the probe) as shown in FIG. put. That is, the upper half of the delay circuit 2, ie, the left half of the array, forms a wavefront 31a, while the lower half of the delay circuit 2, ie, the right half of the array, forms a wavefront 31b. . These two wavefronts converge at points L and R, respectively, as shown. Distance ΔA between L and R
If M is appropriately small, sufficient sound pressure can be obtained even at the intermediate point M.

In this case, if the transmitted waveform is too CW-like, the interference will be significant, so the waveform of the transmitted pulse should be within 2 to 3 cycles at most, as shown in Figure 3 a and b. However, long ones as shown in Fig. 3c and d are not preferred. This is adjusted by the pulse waveform output by the pulsar group.

Even when transmitting waves with a slightly blurred transmission focus in this way, the irradiation is suppressed in areas that deviate from the focal point or the transmitted sound beam, as in the case of transmitting waves with a sharp focus, and the main purpose of selective irradiation is to The process is carried out seamlessly. Within this "blur" range, three received sound rays passing through L, M, and R can be obtained with approximately equal sensitivity as shown in FIG. The bifocal transmission wavefront to be used is dotted line 3 in Figure 2.
It may also be a wavefront such as 2a or 32b.

(Effect of the invention) As explained above, according to the method of the present invention,
By appropriately setting the delay map in the transmission delay circuit to make the transmission wavefront bifocal, and by appropriately setting the distance between the focal points of these wavefronts to a moderate distance, it is possible to improve the selective illumination of the transmission wave and to provide sufficient illumination at long distances. It is possible to realize a transmission method of a polyphonic line receiving sonar that secures energy.

The method of the present invention is applicable to both switched linear scan and phased array sector scan, as well as intermediate and modified versions thereof.
Of course, the present invention can be commonly applied when array probes are used under beamforming using a delay map.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a polyphonic ray receiving sonar according to the method of the present invention, FIG. 2 is a diagram for explaining sound rays, and FIG. 3 is a diagram showing the waveform of a pulse wavefront. . 1... Transmission trigger generator, 2... Transmission beamformer, 3... Pulsar group, 4... Array probe, 5... First stage amplifier group, 6... Variable delay line group, 7... ...logarithmic amplifier, 8...detector, 9...
...Video amplifier, 10...A/D converter, 1
1... Image memory.

Claims (1)

[Claims] 1. In a pulse-echo sonar, there is one delay circuit for transmitting waves consisting of a number of delay lines for individually delaying the pulses that individually drive the many elements of the probe, and the delay circuit for transmitting waves that is It is equipped with a receiving delay circuit for the main sound ray and for the sub-sound ray each consisting of a large number of delay lines for respectively delaying echo signals, and the wavefront of the sound ray transmitted from the probe is approximately a bifocal wavefront. The delay map of the transmitting delay circuit is set so that the delay map for the transmitting delay circuit is set, and the outputs of the receiving delay circuits are combined into one echo signal, and the receiving signals for a total of multiple acoustic scanning lines are simultaneously and independently generated. A sonar that simultaneously receives multiple sound lines.