JPH0693023B2 - Underwater detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an underwater detection apparatus that transmits and receives ultrasonic pulses in a wide range of directions.

<Prior Art> Underwater detection device that transmits and receives ultrasonic pulses in a wide range of directions,
For example, an all-round scanning underwater detection device samples spatial information by rotating and scanning a received beam in an exploration space.

Specifically, the all-round scanning type underwater detection device is equipped with an ultrasonic transducer in which a large number of transducers are arranged in a cylindrical shape, and a drive signal is applied to all of the transducer groups,
The ultrasonic vibration spreads as a disc-shaped beam in the entire circumferential direction. Immediately after this vibration is transmitted, the received signals of the individual transducers are amplified separately, and the phase correction is performed between adjacent transducers to obtain a directivity with a strong receiving sensitivity in a specific direction. A received beam is formed, and reflected waves returning from the respective directions are received by the received beam. By switching the direction of this received beam at high speed and rotating it, scanning of the entire circumference is performed during one vibration transmission period.

<Problems to be Solved by the Invention> By the way, in the above-mentioned all-round scanning type underwater detection apparatus, an image obtained by emitting one ultrasonic pulse is a two-dimensional image along a horizontal plane. In order to obtain a three-dimensional image, it is necessary to emit ultrasonic pulses several times and perform horizontal scanning for each vibration to obtain information on different tilt angles. Since it is transmitted and received several times, there is a problem that it takes time to display a three-dimensional image.

Further, since the detection time is shifted for each tilt direction, there is a problem that a three-dimensional image becomes inaccurate and a sharp image cannot be obtained.

The present invention has been made in view of the above-described problems, and a video image necessary for three-dimensional display can be obtained during one ultrasonic wave oscillation period, so that a high-speed and clear image can be obtained. The purpose is to enable dimensional display.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention has continuously and mutually phase-adjusted with respect to the tilt direction at different frequencies during one vibration period. A drive signal generation circuit for generating drive signals of a predetermined plurality of k types; and an ultrasonic transducer that emits ultrasonic pulses of different frequencies by driving the drive signals toward the tilt angle range of the predetermined plurality of k, respectively. Predetermined plural k for extracting the received signal of the frequency corresponding to each tilt angle range from the received signal of the ultrasonic transmitter / receiver
Of the extraction circuits, a plurality of horizontal beam forming circuits of a predetermined number k for phase-combining the outputs of the extraction circuits in the respective tilt angle ranges to form a horizontal directional received beam, and the received beams. The underwater detection apparatus is configured with a display unit that displays an image based on a received signal in each tilt angle range.

<Operation> According to the above configuration, the ultrasonic wave transmitter / receiver continuously emits ultrasonic wave pulses having different frequencies toward the respective tilt angle ranges during one vibration transmission period. From each tilt angle range, reflected waves with different frequencies come back, and the received signal based on this reflected wave is extracted by each extraction circuit by frequency separation. That is, in each extraction circuit, the received signal in the corresponding tilt angle range is extracted. Then, in the subsequent stage of each extraction circuit, a received beam is formed in the horizontal plane by phase combination with respect to the extracted received signal, and the received signal in the specific horizontal direction is taken in by this received beam. Then, with this received signal, a video signal within each tilt angle range can be obtained. Since these video signals are obtained over the entire range in the tilt direction, this enables a three-dimensional image display.

<Examples> Hereinafter, the present invention will be described in detail based on Examples shown in the drawings.

FIG. 1 is a block diagram showing an entire underwater detection apparatus according to the present invention. This underwater detection apparatus includes an ultrasonic wave transmitter / receiver 1 capable of emitting ultrasonic pulses in a wide range direction and the ultrasonic wave transmitter / receiver. A drive signal generation circuit 2 that generates several types of drive signals (four types in this example) that drive the wave device 1, and a plurality (four in this example) that processes the reception signals from the ultrasonic wave transmitter / receiver 1. The received signal processing units 3 (3 _{1 to} 3 ₄ ) and the display 4 (4 ₁ to 4 ₄ ) for displaying the video signal obtained by each received signal processing unit 3 are provided.

In FIG. 1, 5 is a mixed signal generating circuit for generating a mixed signal for extracting a received signal of a required frequency, and 6 is a phase signal generating circuit for generating a phase control signal for performing phase control on a horizontal plane. , 7 are keying pulse generation circuits.

The drive signal generation circuit 2 reads out the data written in advance in the ROM 8 to continuously drive four types of drive signals having different frequencies and tilted in the tilt direction during one vibration transmission period. A drive signal for generating a signal is supplied to each transducer 1a, ... Of the ultrasonic wave transmitter / receiver 1 via the switch 9. In this example, the drive signals have eight phases in response to the eight transducers 1a arranged in the tilt direction in the ultrasonic wave transmitter / receiver 1. The details of the internal configuration will be described later.

The ultrasonic transmitter / receiver 1 is driven by the drive signal to emit ultrasonic pulses of different frequencies toward a plurality of tilt angle ranges and receive a reflected wave from the angular tilt angle range. Angle Tilt Angle range θ ₁ , θ ₂ , θ
₃ and θ ₄ are obtained by dividing the entire transmission range in advance along the tilt direction, and the number of divisions corresponds to the type of drive signal. That is, the entire transmission range is divided into four along the tilt direction.

Then, received signals based on the reflected waves from the tilt angle range is commonly applied to switching device 9 and four received signals through the amplifier 10 processor 3 ₁ to 3 _4.

When the frequency characteristic of the transducer 1a that constitutes the ultrasonic wave transmitter / receiver 1 is as shown in FIG. 2, for the first tilt angle range θ ₁ close to the horizontal plane, the transducer 1a The frequency f ₁ within the maximum sensitivity range is assigned, and the closer to the tilt angle range that is farther from the horizontal plane,
The frequencies are assigned within the lower sensitivity region of. That is, the first tilt angle range θ ₁ along the horizontal plane has a frequency
f ₁ has a frequency f within the second tilt angle range θ ₂ below
₂ has a frequency f in the third tilt angle range θ ₃ further below.
₃ and the frequency f ₄ is assigned to the lowermost fourth tilt angle range θ ₄ .

Each of the received signal processing units 3 _{1 to} 3 ₄ is for processing the received signal in each tilt angle range, and is an extraction circuit for extracting the received signal of a frequency corresponding to each tilt angle range from the received signal. 11
(11 _{1 to} 11 ₄ ) and a horizontal beam forming circuit 12 (12 _{1 to} 12 ₄ ) for phase-combining the outputs of the extraction circuits 11 to form a directional received beam in a horizontal plane. The internal structure of each received signal processing unit 3, since basically the same, the first for the received signal processing unit 3 ₁ describes the internal structure, the other received signal processing section 3 About _{two or} three ₄ and a detailed description thereof will be omitted.

In the first received signal processing unit 3 _1, extraction circuit 11 _1, the same number as the oscillator 1a for parallel tilt direction (in this example 8
Individual) mixers 13, ... And filters 14 ,. Each mixer 13 mixes the received signal with the mixed signal from the mixed signal generator 5. The mixed signal generation circuit 5 controls the mixer 13 to generate a mixed signal f having a different frequency for each received signal processing unit 3.
Generates _{21 to} f ₂₄ . The mixer 13 mixes the received signal with the mixed signal to convert the received signal into a constant intermediate frequency f ₀ . The filter 14 has a constant frequency f _0.
The received signal corresponding to the predetermined tilt angle range is extracted by passing only the intermediate frequency of.

The output of the filter 14 is input to the horizontal beam forming circuit 12 ₁ . Horizontal beam forming circuit 12 ₁ includes a mixer 15, an adder 16
And a filter 17. The mixer 15 mixes the phase control signal from the phase signal generation circuit 6 and the output of the extraction circuit 111.

The phase signal generation circuit 6 is for generating an n-phase phase control signal having a common frequency and having a phase adjusted in the horizontal direction by reading the data written in advance in the ROM 18, and has an internal configuration of Details will be described later.

The mixer 15 mixes the phase control signals,
Form a received beam. The signals thus phase-synthesized are added by the adder 16 and then passed through the filter 17.

The output of the horizontal beam forming circuit 12 is sent to the CRT through the amplifier 19.
Is supplied to the display device 4 such as. The display 4 is sweep-controlled by a sweep circuit 20 that operates in response to the keying pulse from the keying pulse generating circuit 7.

FIG. 3 is a block diagram of the drive signal generation circuit, and FIG. 4 is its time chart. The drive signal generation circuit 2 is
A first clock pulse generator 21, a gate 22 on the output side of the generator 21, a quaternary counter 23 for counting the first clock pulse supplied through the gate 22, and a count number of the counter 23 Area setting device 24 for switching the read area of the ROM 8. The gate 22 has a fourth
As shown in the figure, in response to the keying pulse a from the keying pulse generating circuit 7, the first clock pulse is led to the quaternary counter 23, and the quaternary counter 23 carries out a closing pulse c to perform a closing operation.

Four storage areas are set in the ROM8, and drive signals in the form of binary signals are stored in each area. The phase of these drive signals is adjusted in advance in the tilt direction.

The drive signal generation circuit 2 also includes a second clock pulse generator 25, a frequency divider 26 that divides the clock pulse in four stages, and a frequency divider that is provided on each output side of the frequency divider 26. .., a decoder 28 for decoding the count output of the quaternary counter 23 and controlling each of the frequency dividing gates 27, ..
A read counter 30 is provided which counts the frequency-divided pulses from the gate 29 and reads the data in any area of the ROM 8 by the count output.

In the ROM8, the frequency of the divided pulse given to the read counter 30 is different every time the read area is different.
Therefore, four kinds of drive signals having different frequencies are continuously output. At the output side of the ROM8, a latch circuit 32, ... Responsive to the latch pulse from the latch pulse generator 31, a gate 34, .. Responsive to a gate pulse from the gate pulse generator 33, an amplifier 35 ,. And are provided.

The gate pulse generator 33, as shown in FIG.
While gate 22 is open for the first clock pulse,
That is, four gate pulses are generated while the data in ROM8 is being read. This gate pulse causes ROM8
Since the gate 35 on the output side of the
Will output four kinds of drive signals one after another as shown in FIG. 4 (e).

FIG. 5 is a block diagram of the phase signal generation circuit. The phase control signal generation circuit 6 includes a third clock pulse generator 37, a frequency divider 38 for dividing the clock pulse,
Read counter 3 that counts the divided clock pulses and reads the data of ROM18 by the count output
9 and. The ROM 18 stores a phase control signal for forming a horizontal receiving beam in the form of a binary signal. On the output side of the ROM 18, a latch circuit 40 that latches read data and a latch pulse generator 41 that supplies a latch pulse to each latch circuit 40 are provided.

According to the above configuration, in the drive signal generation circuit 2, the read area of the ROM 8 is switched and the read timing is changed every time the count number of the quaternary counter 23 is changed. , Four types of drive signals having different frequencies are generated. Ultrasonic transducer 1
Since each transducer 1a is driven by this drive signal, it continuously emits ultrasonic pulses of different frequencies toward each tilt angle range during one vibration transmission period.

Reflected waves with different frequencies return from each tilt angle range, but the received signal based on this reflected wave is separated by frequency separation, and the received signal in the corresponding tilt angle range is extracted by each extraction circuit 11. Will be. That is, in the first extraction circuit 11 ₁ , the received signal of the frequency f ₁ corresponding to the first tilt angle range θ _1, and in the second extraction circuit 11 ₂ corresponds to the second tilt angle range θ ₁ . In the third extraction circuit 11 ₃ , the received signal of frequency f ₂ is received by the third tilt angle range θ ₃
Received signal of a frequency f ₃ corresponding to the fourth extraction circuit 11 ₄
Then, the received signals of the frequency f ₄ corresponding to the fourth tilt angle range θ ₄ are extracted.

Then, in the subsequent stage of each extraction circuit 11, a received beam is formed in the horizontal plane by phase combination with respect to the extracted received signal, and the received signal in the specific horizontal direction is taken in by this received beam. Then, with this received signal, a video signal within each tilt angle range can be obtained. Since these video signals are obtained over the entire range in the tilt direction,
This enables a three-dimensional image display.

By the way, generally, in the all-around scanning underwater detection device, emphasis is placed on horizontal detection, and a detection distance of 400 m in the water depth direction is sufficient. In addition, there is no problem. In the above-mentioned embodiment, the tilt angle range close to the horizontal plane is assigned a frequency within the maximum sensitivity range of the oscillator, and the tilt angle range further away from the horizontal plane has its oscillation frequency at a frequency within the lower sensitivity range of the oscillator. Therefore, the depth detection distance is shorter than the horizontal detection distance. Since the frequency in the high sensitivity region is used for the shallow tilt angle range, the horizontal detection distance is extended to the maximum of the characteristics of the oscillator.

In the illustrated embodiment, the image is displayed on a dedicated display for each tilt angle range, but the images of all tilt angle ranges can be combined and displayed on a single display.

<Effects of the Invention> As described above, according to the present invention, ultrasonic pulses of different frequencies are continuously emitted toward each tilt angle range during one vibration transmission period, and the tilt angle range is changed from each tilt angle range. The received signal based on the returning reflected wave is extracted by frequency separation in each extraction circuit, the received beam is formed by phase combination in the horizontal beam forming circuit, and the received signal in the specific horizontal direction is formed by this received beam. It is captured. Like this one
By transmitting the image once, a video signal along the horizontal direction and the tilt direction can be obtained, which enables a high-speed and clear three-dimensional image display.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an underwater detection apparatus according to the present invention, FIG. 2 is an explanatory diagram showing the relationship between the transmission frequency and the characteristics of a vibrator, and FIG. 3 is a block diagram of a drive signal generation circuit. FIG. 4 is a time chart of the drive signal generation circuit, and FIG. 5 is a block diagram of the phase signal generation circuit. 1 ... Ultrasonic transmitter / receiver, 2 ... Drive signal generation circuit, 3
(3 _{1 to} 3 ₄ ) ... Received signal processing unit, 11 (11 _{1 to} 11 ₄ ) ... Extraction circuit, 12 (12 _{1 to} 12 ₄ ) ... Horizontal beam forming circuit, 4
(4 ₁ to 4 ₄ ) …… Display unit.

Claims (2)

[Claims] 1. A drive signal generation circuit for generating a predetermined plurality of k types of drive signals, which are continuously different in frequency during a single vibration transmission period and are phase-adjusted with respect to each tilt direction, and a transmission signal. An ultrasonic wave transmitter / receiver that emits ultrasonic wave pulses of different frequencies by driving the drive signals toward tilt angle ranges of a plurality of predetermined k, which are obtained by dividing the range along the tilt direction, and a receiver / receiver of the ultrasonic wave transmitter / receiver. A predetermined plurality of extraction circuits for extracting a received signal of a frequency corresponding to each tilt angle range from the wave signal, and the outputs of the extraction circuits are phase-combined, respectively, and the horizontal directivity reception within each tilt angle range is performed. A plurality of horizontal beam forming circuits for forming a wave beam, and a display unit for displaying an image based on a received signal in each tilt angle range received by the directional received beam. Underwater detection system according to claim. 2. A vibration frequency in a tilt angle range near a horizontal plane among vibration vibration frequencies corresponding to each tilt angle range in an ultrasonic wave transmitter / receiver is set within a maximum sensitivity range of a transducer of the ultrasonic wave transmitter / receiver. The underwater detection device according to claim 1, wherein the vibration transmitting frequency is set within a lower sensitivity range of the vibrator as the tilt angle range becomes farther from the horizontal plane.