CN105487077B - Underwater sounding target position estimation method based on laser multipoint coherent detection and device for realizing method - Google Patents

Abstract

An underwater sounding target position estimation method based on laser multipoint coherent detection and a device for realizing the method relate to the underwater sounding target position detection technology. The underwater sounding target position detection method aims at solving the problem that the underwater sounding target position detection cannot be realized by a laser-sound combined detection means. The method comprises the steps of firstly building a laser coherent detection system, then carrying out water surface acoustic wave detection on a plurality of positions of an interested water area by using the coherent detection system, measuring the water surface acoustic wave amplitude of each point by using methods such as frequency spectrum analysis, phase demodulation and the like, and finally considering the position with the maximum amplitude as the optimal estimation of the center of an underwater sound source according to the distribution characteristics of the water surface acoustic wave amplitude. The method and the device can realize the aerial detection of the position of the underwater sound generating source, can select two methods of synchronous multipoint coherent detection or asynchronous multipoint coherent detection according to actual requirements, have very good flexibility and maneuverability, and are suitable for the detection of the underwater sound generating target and the aerial-to-submarine communication.

Description

Method and implementation of underwater sound target position estimation based on laser multi-point coherent detection The means of the method

technical field

The invention relates to an underwater sound target position detection technology.

Background technique

Sonar technology, including underwater sounders, sonobuoys and towed sonars, is still the mainstream technology for underwater sound target detection. For example, sonar technology is used to search for the black box of MH370. The propagation characteristics of sound waves underwater, electronic equipment that completes underwater detection and communication tasks through electro-acoustic conversion and information processing, is divided into two types: active and passive. Due to the poor mobility, flexibility and concealment of shipborne sonar technology, the application of underwater acoustic target detection is limited.

People hope to be able to realize the remote measurement of underwater sound targets, so the "laser-sound" joint detection method is proposed. The current laboratory research shows the potential of the "laser-sound" joint detection technology. The laser coherent detection method has been researched and applied to Some achievements have been made in the extraction of underwater acoustic signals, but the current "laser-acoustic" joint detection method is still unable to detect the location of underwater acoustic targets.

Contents of the invention

The purpose of the present invention is to solve the problem that the "laser-acoustic" joint detection method cannot realize the position detection of the underwater sound target, and provide two methods for estimating the position of the underwater sound target based on laser multi-point coherent detection and the method for realizing the above two methods device.

The first underwater sound target position estimation method based on laser multi-point coherent detection described in the present invention is a synchronous multi-point detection method, which includes the following steps:

Step 1. Randomly select four points on the water surface as detection points, and the four detection points form a square;

Step 2, using the underwater acoustic signal laser coherent detection method to detect the four detection points, respectively obtain the detection signals I _d (t) of the four detection points, that is, the signal received by the photoelectric detector, and detect the four detection points Spectrum analysis or phase demodulation is performed on the detection signal to obtain the amplitude values of the water surface acoustic waves at the four detection points;

Step 3. Determine whether the amplitude values of the water surface acoustic waves at the four detection points are the same. If they are the same, use the detection center, that is, the center point O of the square formed by the four detection points, as the best estimate of the center position of the sound source. If they are not the same , execute step 4;

Step 4. Calculate the moving direction vector of the optical probe of the detection system according to the maximum and second maximum amplitude detection points

Among them, A _max1 is the maximum amplitude value of the water surface acoustic wave at the four detection points, the position corresponding to A _max1 is the detection point S _max1 , A _max2 is the second largest amplitude value of the water surface acoustic wave at the four detection points, and the corresponding position of A _max2 is Detection point S _max2 , O is the center of a square formed by four detection points;

Step 5. According to the vector obtained in step 4 to move the four optical probes, then return to step two.

The device for realizing the above method includes a laser (1), an optical isolator (2), a 1×4 fiber coupler (3), four fiber optic acousto-optic modulators (4), four optical circulators (5), four Probes (6), four optical attenuators (7), four 2×1 couplers (8), 4-channel photodetectors (9) and 4-channel signal demodulation modules (10);

The laser light emitted by the laser (1) enters the 1×4 fiber coupler (3) after passing through the optical isolator (2), and the four output ports of the 1×4 fiber coupler (3) are respectively connected to four fiber optic acousto-optic modulators ( 4) input terminal;

Each optical fiber acousto-optic modulator (4) corresponds to an optical circulator (5), an optical attenuator (7), a 2×1 coupler (8) and a probe (6), and each optical fiber acousto-optic An output end of the modulator (4) is connected to an input end of a 2×1 coupler (8) through an optical attenuator (7), and the other output end of the optical fiber acousto-optic modulator (4) is connected to an optical circulator (5 ), the No. 2 port of the optical circulator (5) is connected to the optical fiber interface of the probe (6), and the No. 3 port of the optical circulator (5) is connected to another input of the 2×1 coupler (8) end;

The output ends of the four 2×1 couplers (8) are connected to the signal input ends of the photodetectors (9), and the output ends of the photodetectors (9) are connected to the signal input ends of the signal demodulation module (10), and the signal demodulation The output end of the module (10) is used for connecting to the upper computer.

The second underwater acoustic target position estimation method based on laser multi-point coherent detection described in the present invention is an asynchronous multi-point detection method. Obtain the detection signal I _d (t) of each detection point, that is, the signal received by the photoelectric detector, and perform spectrum analysis or phase demodulation on the detection signal of each detection point to obtain the amplitude value of the water surface acoustic wave at each detection point , the position of the detection point with the largest amplitude value of the water surface acoustic wave is taken as the best estimate of the center position of the sound source.

The device for realizing the above method includes a laser (1), an optical isolator (2), an optical fiber acousto-optic modulator (4), an optical circulator (5), a probe (6), an optical attenuator (7), and a 2×1 coupling device (8), photodetector (9) and signal demodulation module (10);

The laser light emitted by the laser (1) enters the input end of the optical fiber acousto-optic modulator (4) after passing through the optical isolator (2), and one output end of the optical fiber acousto-optic modulator (4) is connected to 2 × 1 One input end of the coupler (8), the other output end of the optical fiber acousto-optic modulator (4) is connected to the No. 1 port of the optical circulator (5), and the No. 2 port of the optical circulator (5) is connected to the probe (6), the No. 3 port of the optical circulator (5) is connected to another input end of the 2 × 1 coupler (8), and the output end of the 2 × 1 coupler (8) is connected to the photodetector (9 ), the output end of the photodetector (9) is connected to the signal input end of the signal demodulation module (10), and the output end of the signal demodulation module (10) is used to connect to the upper computer.

The present invention proposes a solution to the problem of aerial detection of the location of underwater sound sources. The two methods described in the present invention can be briefly described as the following process: 1) build a laser coherent detection system; 2) use the coherent detection system to detect water surface acoustic waves at multiple locations in the water area of interest; 3) use spectrum analysis, phase The method of demodulation realizes the measurement of the amplitude of the water surface acoustic wave at each point; 4) According to the distribution characteristics of the amplitude of the water surface acoustic wave, the position with the largest amplitude is regarded as the optimal estimate of the center of the underwater sound source.

According to the basic principle of the underwater acoustic target position assessment method of basic multipoint coherent detection, its implementation method can adopt two forms: 1) synchronous multipoint detection; 2) asynchronous multipoint detection.

The method and device of the present invention can realize the aerial detection of the location of the underwater sound source, and two methods of synchronous multi-point coherent detection or asynchronous multi-point coherent detection can be selected according to actual needs. The flexibility and maneuverability are very good, and it is suitable for underwater Down-emitting acoustic target detection, and air-to-submarine communications.

Description of drawings

Fig. 1 is the spatial shape diagram of the water surface acoustic wave in the first embodiment;

2 is a schematic diagram of the basic principle of laser coherent detection of underwater acoustic signals in Embodiment 1. 11 represents a beam splitter, 12 represents a plane mirror, 13 represents a signal generator, 14 represents a power amplifier, 15 represents an underwater sound source, 16 Indicates the data acquisition and processing system;

Fig. 3 is an initial position distribution diagram of four detection points in Embodiment 1;

Fig. 4 is a schematic diagram of sound source center positioning in Embodiment 1;

Fig. 5 is a flowchart of the method described in Embodiment 1;

Fig. 6 is a functional block diagram of obtaining water surface acoustic wave information according to coherent signals in Embodiment 2;

Fig. 7 is a schematic structural diagram of the device described in Embodiment 5;

Fig. 8 is a schematic structural diagram of the device described in Embodiment 7.

detailed description

Specific Embodiment 1: This embodiment is described in conjunction with FIGS. 1 to 5. The method for estimating the position of an underwater sounding target based on laser multi-point coherent detection described in this embodiment is a synchronous multi-point detection method. The method is:

Step 1. Randomly select four points on the water surface as detection points, and the four detection points form a square;

Step 2, using the underwater acoustic signal laser coherent detection method to detect the four detection points, respectively obtain the detection signals I _d (t) of the four detection points, that is, the signal received by the photoelectric detector, and detect the four detection points Spectrum analysis or phase demodulation is performed on the detection signal to obtain the amplitude values of the water surface acoustic waves at the four detection points;

Step 3. Determine whether the amplitude values of the water surface acoustic waves at the four detection points are the same. If they are the same, use the detection center, that is, the center point O of the square formed by the four detection points, as the best estimate of the center position of the sound source. If they are not the same , execute step 4;

Step 4. Calculate the moving direction vector of the optical probe of the detection system according to the maximum and second maximum amplitude detection points

Among them, A _max1 is the maximum amplitude value of the water surface acoustic wave at the four detection points, the position corresponding to A _max1 is the detection point S _max1 , A _max2 is the second largest amplitude value of the water surface acoustic wave at the four detection points, and the position corresponding to A _max2 is Detection point S _max2 , O is the center of a square formed by four detection points;

Step 5. According to the vector obtained in step 4 to move the four optical probes, then return to step two.

The water surface acoustic wave is a kind of transverse micro-amplitude wave caused by underwater acoustic radiation penetrating the water-air interface. If the center of the sound source disturbance on the water surface is taken as the coordinate origin and the normal direction of the water surface is used as the Z coordinate axis to establish a coordinate system, then according to the liquid According to the surface transverse micro-amplitude wave theory, the three-dimensional traveling wave solution of the water surface acoustic wave can be expressed by the following formula:

In the formula, η is the real-time amplitude of the water surface acoustic wave at the position (x, y), j is the imaginary number symbol, x is the X-axis coordinate component, y is the Y-axis coordinate component, and ω is the angular frequency of the water surface acoustic wave (that is, the underwater angular frequency of the acoustic signal), and e is the base of the natural logarithm.

Due to the viscous effect of water, the amplitude of the transverse micro-amplitude wave on the water surface cannot remain unchanged, that is, the range of the transverse micro-amplitude wave on the water surface is not infinite, and the amplitude of the micro-amplitude wave on the water surface decreases with the increase of the propagation distance. Small, that is, the closer the particle in the micro-amplitude wave region of the water surface is to the disturbance source, the larger the amplitude will be. Studies have shown that the amplitude of the transverse micro-amplitude wave on the water surface will decay exponentially, so the above formula can be modified as:

In the formula, τ is the attenuation coefficient. Therefore, the spatial shape of the water surface acoustic wave caused by underwater acoustic radiation is shown in Fig. 1. The entire waveform presents a concentric circle structure with a large center amplitude and a small outer edge amplitude. The center of the concentric circles is the location of the underwater sound radiation center. It is precisely because of the characteristics of the amplitude attenuation of the transverse micro-amplitude wave on the water surface that we can use the method of multi-point amplitude detection to realize the estimation of the sound position of the underwater target.

The principle of laser coherent detection of underwater acoustic signals is shown in Figure 2, which is a typical optical path diagram of laser coherent detection of underwater acoustic signals. The laser beam emitted by the laser is diffracted by the acousto-optic modulator (AOM), and then split into two beams, one beam is used as the measurement beam, and the other beam is used as the reference beam. The measurement light is directly incident on the water surface to be measured. The vibration of the water surface contains vibration components of the same frequency as the underwater sound source because of the modulation of the underwater sound source. The light spot with small light intensity around it) enters the beam splitter and is reflected by the beam splitter; the reference light is reflected by the 45-degree flat mirror, enters the beam splitter, and is transmitted through the beam splitter. Inside the beam splitter, the measurement light and the reference light The light merges, coherence occurs, and the coherent light is incident on the detection surface of the photodetector. The photodetector receives the coherent signal and converts it into an electrical signal. After the electrical signal is processed by the signal processing circuit and the data acquisition and processing system, it is read by the host computer, and the coherent signal read by the host computer is further processed to be decipherable. Call out the characteristics of the underwater acoustic signal.

The distribution of the four detection points S ₁ , S ₂ , S ₃ , and S ₄ of the synchronous multi-point coherent detection method is shown in Figure 3. The overall shape is a square, and its geometric center is point O. In practice, use the synchronous multi-point coherent detection system to conduct multi-point detection on the water area of interest, obtain the water surface acoustic wave information at the four detection points S ₁ , S ₂ , S ₃ , and S ₄ , and select the water surface acoustic wave with the largest amplitude and the second-largest two detection positions, respectively denoted as S _max1 and S _max2 , then the center direction of the sound source is within the angular range formed by the detection point S _{max1 with the largest amplitude, the second-largest detection point S max2 and} the central point O. Taking Figure 3 as an example, the detection point with the largest amplitude of the acoustic wave on the water surface is S ₁ , and the second largest detection point is S ₄ , then the direction of the sound source center C relative to the detection system then in the vector with Between. In order to search for the maximum amplitude position of the water surface acoustic wave, the detection system needs to follow the direction Move and constantly adjust the position of the detection system so that the amplitudes of the water surface acoustic waves detected by the four detection points are basically the same, as shown in Figure 4. At this time, the detection center point O is considered to be the optimal estimate of the sound source center.

Specific Embodiment 2: This embodiment is described in conjunction with FIG. 6. This embodiment is a further limitation of the underwater sound target position estimation method based on laser multi-point coherent detection described in Embodiment 1. According to Embodiment 1 Measuring principle, the acquisition method of the detection signal I _d (t) in step 2 is:

The distribution of the light amplitude E _b of the reference light with time t is:

E _b (t)＝A _b sin(ω ₀ t+kz _b +φ) (1)

In the formula, A _b is the amplitude of the reference light amplitude E _b ;

ω ₀ is the laser angular frequency;

k is the laser wave number;

z _b is the optical path of the reference light;

φ is the initial phase of the laser.

The distribution of the light amplitude E _m of the measured light over time t is:

E _m (t)＝A _m sin[(ω ₀ +ω _d )t+kz _m +φ] (2)

In the formula, A _m is the amplitude of the measured light amplitude E _b ;

z _m is the optical path of the measuring light;

ω _d is the modulation frequency of the AOM.

The combined amplitude of the reference light and measuring light is:

E(t)＝E _b (t)+E _m (t)＝A _m sin(ω ₀ t+kz _m +φ)+A _b sin[(ω ₀ +ω _d )t+kz _b +φ] ( 3)

Then the coherent light intensity I(t) is:

The light intensity is received by the photodetector, which does not respond to high-frequency terms, that is, A _m ² cos ² (ω ₀ t+kz _m +φ), A _b ² cos ² [(ω ₀ +ω _d )t+kz _b +φ], and A _m A _b cos[(2ω ₀ +ω _d )t+kz _m +kz _b +2φ] are transformed into DC signals, therefore, the light intensity signal I _d after removing the DC component is expressed as:

I _d (t)＝KA _m A _b cos[k(z _m -z _b )]＝A _d cos[ω _d t+k(z _m -z _b )] (5)

In the formula, K is the magnification of the photoelectric receiver, write A _d ＝KA _m A _b ,

It can be seen from the above formula that the signal received by the photodetector is a modulation signal about the optical path difference between the reference light and the measuring light. The optical path difference of the two laser beams is related to the initial length of the two arms and the vibration of the water surface, where the vibration of the water surface includes There are two parts of the natural water surface fluctuation and the water surface acoustic wave excited by the underwater acoustic signal. Therefore, the optical path difference z _m -z _b is expressed as:

z _m -z _b ＝2(L ₁ -L ₂ )+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s ) (6)

In the formula, A _n sin(2πf _n t+φ _n ) is the vibration expression of the natural water surface (A _n is the amplitude of the natural water surface, f _n is the vibration frequency of the natural water surface, and φ _n is the initial phase of the natural water surface vibration) , A _s sin(2πf _s t+φ _s ) is the expression of water surface vibration caused by underwater sound source (A _s is the amplitude of water surface acoustic wave, f _s is the frequency of water surface acoustic wave vibration, φ _s is the initial value of water surface acoustic wave vibration phase), L ₁ is the initial optical path length of the measuring light when the water surface is stationary, L ₂ is the optical path length of the reference light when the water surface is stationary, then (L ₁ -L ₂ ) is the initial optical path difference of the two paths of light when the water surface is stationary, Denoted as ΔL, the light intensity signal received by the photodetector can be expressed by the following formula:

I _d (t)＝A _d cos{ω _d t+k[2△L+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s )]} (7)

A _s sin(2πf _s t+φ _s ) is the information of the water surface acoustic wave caused by the underwater sound source.

It can be seen from the formula (7) that the phase of the detection signal obtained by the photodetector contains the information of the water surface acoustic wave caused by the underwater sound source: As sin(2πf _{s t+φ s )} . The vibration amplitude A _s and vibration frequency f _s of the water surface acoustic wave can be obtained by analyzing the detection signal by conventional methods (such as spectrum analysis or phase demodulation). The principle shown in Figure 6 can be used to obtain water surface acoustic wave information: A _s sin(2πf _s t+φ _s ).

Specific Embodiment Three: The method for estimating the position of an underwater sounding target based on laser multi-point coherent detection described in this embodiment is an asynchronous multi-point detection method. Point detection, to obtain the detection signal I _d (t) of each detection point, that is, the signal received by the photoelectric detector, and perform spectrum analysis or phase demodulation on the detection signal of each detection point, and obtain the water surface of each detection point Acoustic amplitude value, the position of the detection point with the largest acoustic wave amplitude value on the water surface is used as the best estimate of the center position of the sound source.

Specific embodiment four: this embodiment is the further limitation to the underwater sound target position estimation method based on laser multi-point coherent detection described in embodiment three, the acquisition method of detection signal I _d (t) is:

The distribution of the light amplitude E _b of the reference light with time t is:

E _b (t)＝A _b sin(ω ₀ t+kz _b +φ) (1)

In the formula, A _b is the amplitude of the reference light amplitude E _b ;

ω ₀ is the laser angular frequency;

k is the laser wave number;

z _b is the optical path of the reference light;

φ is the initial phase of the laser.

The distribution of the light amplitude E _m of the measured light over time t is:

E _m (t)＝A _m sin[(ω ₀ +ω _d )t+kz _m +φ] (2)

In the formula, A _m is the amplitude of the measured light amplitude E _b ;

z _m is the optical path of the measuring light;

ω _d is the modulation frequency of the AOM.

The combined amplitude of the reference light and measuring light is:

E(t)＝E _b (t)+E _m (t)＝A _m sin(ω ₀ t+kz _m +φ)+A _b sin[(ω ₀ +ω _d )t+kz _b +φ] ( 3)

Then the coherent light intensity I(t) is:

The light intensity is received by the photodetector, which converts A _m ² cos ² (ω ₀ t+kz _m +φ), A _b ² cos ² [(ω ₀ +ω _d )t+kz _b +φ], and Am A _b cos[(2ω ₀ +ω _d ) _{t+kz m +} kz _b +2φ] is transformed into a DC signal, therefore, the light intensity signal I _d after removing the DC component is expressed as:

I _d (t)＝KA _m A _b cos[k(z _m -z _b )]＝A _d cos[ω _d t+k(z _m -z _b )] (5)

In the formula, K is the magnification of the photoelectric receiver, write A _d ＝KA _m A _b ,

The optical path difference z _m -z _b is expressed as:

z _m -z _b ＝2(L ₁ -L ₂ )+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s ) (6)

In the formula, A _n sin(2πf _n t+φ _n ) is the vibration expression of the natural water surface (A _n is the amplitude of the natural water surface, f _n is the vibration frequency of the natural water surface, and φ _n is the initial phase of the natural water surface vibration) , A _s sin(2πf _s t+φ _s ) is the expression of water surface vibration caused by underwater sound source (A _s is the amplitude of water surface acoustic wave, f _s is the frequency of water surface acoustic wave vibration, φ _s is the initial value of water surface acoustic wave vibration phase), L ₁ is the initial optical path length of the measuring light when the water surface is stationary, L ₂ is the optical path length of the reference light when the water surface is stationary, then (L ₁ -L ₂ ) is the initial optical path difference of the two paths of light when the water surface is stationary, Denoted as ΔL, the light intensity signal received by the photodetector can be expressed by the following formula:

I _d (t)＝A _d cos{ω _d t+k[2△L+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s )]} (7)

A _s sin(2πf _s t+φ _s ) is the information of the water surface acoustic wave caused by the underwater sound source.

Specific embodiment five: This embodiment is described in conjunction with FIG. 6 and FIG. 7. This embodiment is a device for realizing the method for estimating the position of an underwater sounding target based on laser multi-point coherent detection described in Embodiment 2. The device includes a laser ( 1), optical isolator (2), 1×4 fiber coupler (3), four fiber optic acousto-optic modulators (4), four optical circulators (5), four probes (6), four optical Attenuator (7), four 2×1 couplers (8), 4-channel photodetector (9) and 4-channel signal demodulation module (10);

The laser light emitted by the laser (1) enters the 1×4 fiber coupler (3) after passing through the optical isolator (2), and the four output ports of the 1×4 fiber coupler (3) are respectively connected to four fiber optic acousto-optic modulators ( 4) input terminal;

Each optical fiber acousto-optic modulator (4) corresponds to an optical circulator (5), an optical attenuator (7), a 2×1 coupler (8) and a probe (6), and each optical fiber acousto-optic An output end of the modulator (4) is connected to an input end of a 2×1 coupler (8) through an optical attenuator (7), and the other output end of the optical fiber acousto-optic modulator (4) is connected to an optical circulator (5 ), the No. 2 port of the optical circulator (5) is connected to the optical fiber interface of the probe (6), and the No. 3 port of the optical circulator (5) is connected to another input of the 2×1 coupler (8) end;

The output ends of the four 2×1 couplers (8) are connected to the signal input ends of the photodetectors (9), and the output ends of the photodetectors (9) are connected to the signal input ends of the signal demodulation module (10), and the signal demodulation The output end of the module (10) is used for connecting to the upper computer.

Figure 7 is a schematic diagram of the structure of the device for realizing the synchronous multi-point detection method: the laser with a pigtail (1) outputs a single-frequency laser beam, which is input to the 1×4 fiber coupler (3) after passing through the optical isolator (2) Inside, the 1×4 fiber optic coupler (3) outputs 4 lasers at equal light intensity, and the 4 lasers are respectively input to the optical fiber acousto-optic modulator (4), and the 0-order light output by the optical fiber acousto-optic modulator (4) is used as The reference light, the first-class light output by it is used as the detection light: the 4-way detection light is output to the 4 probes (6) through the optical circulator (5), and the 4 probes (6) emit the detection laser light to the water area to be detected, and receive The laser beam reflected back from the water surface is the reflected laser beam. The phase of the reflected laser beam is modulated by the fluctuation of the water surface. The reflected laser beam is input to the 2×1 coupler (8) after passing through the circulator; After passing through the optical attenuator (7), it is also input to the 2×1 coupler (8), and the coherent signal is generated after the combination of the two beams of light. The 4-way coherent signal is received by the 4-channel photodetector (9), and the photodetector ( 9) convert the coherent signal into an electrical signal, enter the signal demodulation module (10) of 4 channels, and the signal demodulation module (10) uses the principle shown in Figure 6 to process the received signal to obtain the water surface acoustic wave information A _s sin(2πf _s t+φ _s ), send this information to the host computer, and the host computer can obtain the information of the water surface acoustic waves at the 4 detection points.

Embodiment 6: This embodiment is described in conjunction with FIG. 7. This embodiment is a further limitation to the device described in Embodiment 5. In this embodiment, the probe (6) includes a multi-mirror optical coupler and a fixed-focus lens. The optical fiber interface of the multi-mirror optical coupler is used as the optical fiber interface of the probe (6). The probe light is incident on the water surface after passing through the multi-mirror optical coupler and the fixed-focus lens in sequence, and the laser light returned through the water surface passes through the fixed-focus lens and the multi-lens lens in sequence After the optical coupler, enter the No. 2 port of the optical circulator (5).

The fiber optic coupler is used to emit the detection laser to the water area to be detected, and at the same time cooperate with the fixed-focus lens to realize the reception of the reflected laser beam.

Specific Embodiment Seven: This embodiment is described in conjunction with FIG. 8. This embodiment is a device for realizing the method for estimating the position of an underwater sounding target based on laser multi-point coherent detection described in Embodiment 4. The device includes a laser (1), Optical isolator (2), optical fiber acousto-optic modulator (4), optical circulator (5), probe (6), optical attenuator (7), 2×1 coupler (8), photodetector (9) And signal demodulation module (10);

The laser light emitted by the laser (1) enters the input end of the optical fiber acousto-optic modulator (4) after passing through the optical isolator (2), and one output end of the optical fiber acousto-optic modulator (4) is connected to 2 × 1 One input end of the coupler (8), the other output end of the optical fiber acousto-optic modulator (4) is connected to the No. 1 port of the optical circulator (5), and the No. 2 port of the optical circulator (5) is connected to the probe (6), the No. 3 port of the optical circulator (5) is connected to another input end of the 2 × 1 coupler (8), and the output end of the 2 × 1 coupler (8) is connected to the photodetector (9 ), the output end of the photodetector (9) is connected to the signal input end of the signal demodulation module (10), and the output end of the signal demodulation module (10) is used to connect to the upper computer.

The device uses an optical probe to detect water surface acoustic waves point by point in the water area of interest, and takes the point of maximum amplitude as the optimal estimation of the center position of the sound source.

Embodiment 8: This embodiment is described in conjunction with FIG. 8. This embodiment is a further limitation of the device described in Embodiment 7. In this embodiment, the probe (6) includes a multi-mirror optical coupler and a fixed-focus lens. The optical fiber interface of the multi-mirror optical coupler is used as the optical fiber interface of the probe (6). The probe light is incident on the water surface after passing through the multi-mirror optical coupler and the fixed-focus lens in sequence, and the laser light returned through the water surface passes through the fixed-focus lens and the multi-lens lens in sequence After the optical coupler, enter the No. 2 port of the optical circulator (5).

The fiber optic coupler is used to emit the detection laser to the water area to be detected, and at the same time cooperate with the fixed-focus lens to realize the reception of the reflected laser beam.

Claims (4)

1. The underwater sound target position estimation method based on laser multi-point coherent detection, it is characterized in that, this method is: Step 1. Randomly select four points on the water surface as detection points, and the four detection points form a square; Step 2, using the underwater acoustic signal laser coherent detection method to detect the four detection points, respectively obtain the detection signals I _d (t) of the four detection points, that is, the signal received by the photoelectric detector, and detect the four detection points Spectrum analysis or phase demodulation is performed on the detection signal to obtain the amplitude values of the water surface acoustic waves at the four detection points; Step 3. Determine whether the amplitude values of the water surface acoustic waves at the four detection points are the same. If they are the same, use the detection center, that is, the center point O of the square formed by the four detection points, as the best estimate of the center position of the sound source. If they are not the same , execute step 4; Step 4. Calculate the moving direction vector of the optical probe of the detection system according to the maximum and second maximum amplitude detection points Among them, A _max1 is the maximum amplitude value of the water surface acoustic wave at the four detection points, the position corresponding to A _max1 is the detection point S _max1 , A _max2 is the second largest amplitude value of the water surface acoustic wave at the four detection points, and the position corresponding to A _max2 is Detection point S _max2 , O is the center of a square formed by four detection points; Step 5. According to the vector obtained in step 4 to move the four optical probes, then return to step two. 2. the underwater sound target position estimation method based on laser multipoint coherent detection according to claim 1, is characterized in that, the acquisition method of the detection signal I _d (t) in step 2 is: The distribution of the light amplitude E _b of the reference light with time t is: E _b (t)＝A _b sin(ω ₀ t+kz _b +φ) (1) In the formula, A _b is the amplitude of the reference light amplitude E _b ; ω ₀ is the laser angular frequency; k is the laser wave number; z _b is the optical path of the reference light; φ is the initial phase of the laser; The distribution of the light amplitude E _m of the measured light over time t is: E _m (t)＝A _m sin[(ω ₀ +ω _d )t+kz _m +φ] (2) In the formula, A _m is the amplitude of the measured light amplitude E _b ; z _m is the optical path of the measuring light; ω _d is the modulation frequency of the AOM; The combined amplitude of the reference light and measuring light is: E(t)＝E _b (t)+E _m (t)＝A _m sin(ω ₀ t+kz _m +φ)+A _b sin[(ω ₀ +ω _d )t+kz _b +φ] ( 3) Then the coherent light intensity I(t) is: <mrow><mtable><mtr><mtd><mrow><mi>I</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>=</mo><mo>|</mo><mi>E</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><msup><mo>|</mo><mn>2</mn></msup><mo>=</mo><msup><msub><mi>A</mi><mi>m</mi></msub><mn>2</mn></msup><msup><mi>cos</mi><mn>2</mn></msup><mrow><mo>(</mo><msub><mi>&amp;omega;</mi><mn>0</mn></msub><mi>t</mi><mo>+</mo><msub><mi>kz</mi><mi>m</mi></msub><mo>+</mo><mi>&amp;phi;</mi><mo>)</mo></mrow><mo>+</mo><msup><msub><mi>A</mi><mi>b</mi></msub><mn>2</mn></msup><msup><mi>cos</mi><mn>2</mn></msup><mo>&amp;lsqb;</mo><mrow><mo>(</mo><msub><mi>&amp;omega;</mi><mn>0</mn></msub><mo>+</mo><msub><mi>&amp;omega;</mi><mi>d</mi></msub><mo>)</mo></mrow><mi>t</mi><mo>+</mo><msub><mi>kz</mi><mi>b</mi></msub><mo>+</mo><mi>&amp;phi;</mi><mo>&amp;rsqb;</mo></mrow></mtd></mtr><mtr><mtd><mrow><mo>+</mo><msub><mi>A</mi><mi>m</mi></msub><msub><mi>A</mi><mi>b</mi></msub><mi>cos</mi><mo>&amp;lsqb;</mo><mrow><mo>(</mo><mn>2</mn><msub><mi>&amp;omega;</mi><mn>0</mn></msub><mo>+</mo><msub><mi>&amp;omega;</mi><mi>d</mi></msub><mo>)</mo></mrow><mi>t</mi><mo>+</mo><msub><mi>kz</mi><mi>m</mi></msub><mo>+</mo><msub><mi>kz</mi><mi>b</mi></msub><mo>+</mo><mn>2</mn><mi>&amp;phi;</mi><mo>&amp;rsqb;</mo><mo>+</mo><msub><mi>A</mi><mi>m</mi></msub><msub><mi>A</mi><mi>b</mi></msub><mi>cos</mi><mo>&amp;lsqb;</mo><msub><mi>&amp;omega;</mi><mi>d</mi></msub><mi>t</mi><mo>+</mo><mi>k</mi><mrow><mo>(</mo><msub><mi>z</mi><mi>m</mi></msub><mo>-</mo><msub><mi>z</mi><mi>b</mi></msub><mo>)</mo></mrow><mo>&amp;rsqb;</mo></mrow></mtd></mtr></mtable><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>4</mn><mo>)</mo></mrow></mrow> The light intensity is received by the photodetector, which converts A _m ² cos ² (ω ₀ t+kz _m +φ), A _b ² cos ² [(ω ₀ +ω _d )t+kz _b +φ], and Am A _b cos[(2ω ₀ +ω _d ) _{t+kz m +} kz _b +2φ] is transformed into a DC signal, therefore, the light intensity signal I _d after removing the DC component is expressed as: I _d (t)＝KA _m A _b cos[k(z _m -z _b )]＝A _d cos[ω _d t+k(z _m -z _b )] (5) In the formula, K is the magnification of the photoelectric receiver, write A _d ＝KA _m A _b , The optical path difference z _m -z _b is expressed as: z _m -z _b ＝2(L ₁ -L ₂ )+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s ) (6) In the formula, A _n sin(2πf _n t+φ _n ) is the vibration expression of the natural water surface, A _n is the amplitude of the natural water surface, f _n is the vibration frequency of the natural water surface, φ _n is the initial phase of the natural water surface vibration, A _s sin(2πf _s t+φ _s ) is the expression of the water surface vibration caused by the underwater sound source, A _s is the amplitude of the water surface acoustic wave, f _s is the vibration frequency of the water surface acoustic wave, and φ _s is the initial phase of the water surface acoustic vibration , L ₁ is the initial optical path length of the measurement light when the water surface is still, L ₂ is the optical path length of the reference light when the water surface is still, then (L ₁ -L ₂ ) is the initial optical path difference of the two lights when the water surface is still, denoted as ΔL, the light intensity signal received by the photodetector can be expressed by the following formula: I _d (t)＝A _d cos{ω _d t+k[2ΔL+2A _n sin(2πf _n t+φ _n )+2A _s sin(2πf _s t+φ _s )]} (7) A _s sin(2πf _s t+φ _s ) is the information of the water surface acoustic wave caused by the underwater sound source. 3. realize the device of the underwater sound target position estimation method based on laser multipoint coherent detection claimed in claim 2, it is characterized in that, described device comprises laser device (1), optical isolator (2), 1 * 4 optical fiber Couplers (3), four fiber optic acousto-optic modulators (4), four optical circulators (5), four probes (6), four optical attenuators (7), four 2×1 couplers ( 8), 4-channel photodetector (9) and 4-channel signal demodulation module (10); The laser light emitted by the laser (1) enters the 1×4 fiber coupler (3) after passing through the optical isolator (2), and the four output ports of the 1×4 fiber coupler (3) are respectively connected to four fiber optic acousto-optic modulators ( 4) input terminal; Each optical fiber acousto-optic modulator (4) corresponds to an optical circulator (5), an optical attenuator (7), a 2×1 coupler (8) and a probe (6), and each optical fiber acousto-optic An output end of the modulator (4) is connected to an input end of a 2×1 coupler (8) through an optical attenuator (7), and the other output end of the optical fiber acousto-optic modulator (4) is connected to an optical circulator (5 ), the No. 2 port of the optical circulator (5) is connected to the optical fiber interface of the probe (6), and the No. 3 port of the optical circulator (5) is connected to another input of the 2×1 coupler (8) end; The output ends of the four 2×1 couplers (8) are connected to the signal input ends of the photodetectors (9), and the output ends of the photodetectors (9) are connected to the signal input ends of the signal demodulation module (10), and the signal demodulation The output end of the module (10) is used for connecting to the upper computer. 4. the device of realizing the underwater sound target position estimation method based on laser multi-point coherent detection according to claim 3, is characterized in that, described probe (6) comprises multi-mirror optical coupler and fixed-focus lens, and multi-mirror The optical fiber interface of the optical coupler is used as the optical fiber interface of the probe (6). The probe light is incident on the water surface after passing through the multi-mirror optical coupler and the fixed-focus lens in sequence. Enter the No. 2 port of the optical circulator (5) after the circulator.