CN210864039U - Underwater target detection system based on laser acoustic scanning mode - Google Patents

Abstract

The utility model provides an underwater target detection system based on a laser-induced acoustic scanning method. The system includes: laser, optical shaping unit, scanning galvanometer, field lens, hydrophone and host computer. The laser generated by the laser passes through the optical shaping unit, scanning galvanometer, and field mirror in sequence, and then is injected into the water and focused underwater, so that the water medium produces a photoacoustic effect, radiating sound waves to the surrounding, and the sound waves are reflected by the underwater target object and then heard by the water. The hydrophone is used to convert the received sound wave signal into an electrical signal and send it to the upper computer; the upper computer is connected to the laser and the scanning galvanometer in communication, which can control the laser output of the laser and the deflection of the scanning galvanometer; the upper computer The computer obtains the acoustic signal by adjusting the electrical signal sent by the hydrophone, and calculates and processes the adjusted acoustic signal to obtain the depth and orientation of the underwater detected target object. The technical scheme of the utility model has the characteristics of strong mobility, high sensitivity and large detection range.

Description

Underwater target detection system based on laser acoustic scanning

technical field

The utility model relates to the technical field of underwater detection and communication, in particular to an underwater target detection system based on a laser-induced acoustic scanning method.

Background technique

At present, there are two main methods for underwater target detection: optical detection and acoustic detection. Optical detection mainly uses imaging methods to detect underwater targets. Then underwater, the propagation of the light wave is very attenuated, and the distance to travel and measure is limited. In contrast, sound waves propagate better in water. After encountering an underwater target, the sound wave has a large reflection coefficient, which is beneficial to obtain object information. In traditional acoustic wave measurement, sonar sensors are widely used as receiving sensors. However, the sonar sensors themselves have the disadvantages of low detection accuracy, high power consumption, large weight, large space and inconvenience for mobile detection.

Utility model content

In view of the above-mentioned defects of the prior art, the present invention provides an underwater target detection system based on a laser-induced acoustic scanning method.

In one aspect, the present invention provides an underwater target detection system based on a laser-induced acoustic scanning method, comprising: a laser, an optical shaping unit, a scanning galvanometer, a field mirror, a hydrophone and a host computer;

The laser is used as a light source to generate laser light; the optical shaping unit is used to adjust the laser light generated by the laser;

The laser light generated by the laser passes through the optical shaping unit, the scanning galvanometer, and the field mirror in sequence, and then is injected into the water and focused underwater, so that the water medium produces a photoacoustic effect and radiates sound waves to the surrounding. The hydrophone is received, and the hydrophone is used to convert the received sound wave signal into an electrical signal and send it to the upper computer;

The host computer is connected in communication with the laser and the scanning galvanometer; the host computer is used to control the laser output of the laser and the deflection of the scanning galvanometer;

The host computer is also used to adjust the electrical signal sent by the hydrophone to obtain an acoustic signal, and to calculate and process the adjusted acoustic signal to obtain the depth and orientation of the underwater detected target object.

In the above system, preferably, the laser is a solid-state pulsed laser; the laser wavelength generated by the solid-state pulsed laser is 1064 nm, the output energy is ≧400 mJ, the repetition frequency is 1-10 Hz, and the pulse width is 6-8 ns.

In the above system, preferably, the scanning galvanometer includes: an X scanning motor, an X scanning mirror, a Y scanning motor and a Y scanning mirror, the X scanning motor is used to drive the X scanning mirror to deflect, and the Y scanning motor is used to drive the Y scanning mirror Scanning mirror deflection.

In the above system, preferably, the X scanning mirror and the Y scanning mirror are reflecting mirrors.

The system as described above, wherein the optical shaping unit is used to adjust the laser light generated by the laser, including:

Adjust the laser transmission direction and beam diameter generated by the laser, and adjust the laser beam divergence angle.

In the above system, preferably, the laser is pumped by a xenon lamp to generate laser light.

On the other hand, the present invention provides an underwater target detection method based on a laser-induced acoustic scanning method, comprising:

Set the laser, optical shaping unit, scanning galvanometer and field mirror on the water platform, and set the hydrophone in the water;

Use the laser to generate the laser signal, and adjust the positional relationship between the laser, the optical shaping unit, the scanning galvanometer, and the field mirror, so that the laser signal generated by the laser passes through the optical shaping unit, the scanning galvanometer, and the field mirror in sequence, and then is injected into the water and is in the water. Underwater focusing, making the water medium produce photoacoustic effect, radiating sound waves to the surrounding;

Adjust the position of the hydrophone in the water, so that the sound wave is received by the hydrophone after being reflected by the underwater target object;

The hydrophone converts the received sound wave signal into an electrical signal and sends it to the upper computer;

The host computer receives the electrical signal sent by the hydrophone, and adjusts the electrical signal into an acoustic signal;

The host computer processes the acoustic signal to obtain the depth and orientation of the underwater detected target object.

The method as described above, further comprising:

Use the host computer to control the deflection of the scanning galvanometer, and use the laser scanning method to make the spot at the laser focus move in a regular shape or a specific direction in the same plane at different speeds, so that the acoustic waves generated on the scanning path are coherently superimposed during the propagation process. The sound waves are reflected by the underwater target and received by the hydrophone.

The method as above, wherein, the upper computer processes the acoustic signal, including:

The host computer uses the correlation method, the difference method and the Gauss-Newton iterative algorithm to process the acoustic signal.

The technical scheme provided by the utility model utilizes the laser to generate the sound source, converts the laser energy into the sound wave energy, uses the laser scanning method, and utilizes the characteristics of the low attenuation coefficient of the laser in the air and the long propagation distance, which can be generated in a wider range. The sound source can increase the effective propagation distance of sound waves in water. The Doppler effect can also be generated by the movement of the sound source, which can obtain a wider sound signal spectrum, control the moving speed of the laser focusing spot, and encode the sound wave signal for laser induction. sound communication. The scanning galvanometer is used to make the laser form a series of sound waves on the scanning path of the spot. After the sound waves are superimposed coherently, the propagation range can be greatly increased in a specific direction, thereby expanding the detection range. It overcomes the shortcomings of high-frequency waves in water with large attenuation rate and small measurement range, and also overcomes the shortcomings of sonar sensors in traditional acoustic detection, and has the advantages of strong mobility and high sensitivity. In addition, the technical solution provided by the present utility model adopts the laser acoustic system to generate the sound source signal, and the generated acoustic signal has the advantages of high sound pressure level, wide frequency spectrum, non-contact control, etc., and the used hydrophone has a watertight structure. Good, anti-corrosion, small size, strong mobility, high sensitivity.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only for the present invention. For some embodiments of the present invention, for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic diagram of an underwater target detection system based on a laser-induced acoustic scanning method provided by the utility model;

2 is a flowchart of an underwater target detection method based on a laser-induced acoustic scanning method provided by the utility model;

3 is a schematic diagram of a laser scanning method in the technical solution provided by the utility model;

4 is a schematic diagram of the coherent superposition of acoustic waves in the technical solution provided by the utility model;

5 is a schematic diagram of the hydrophone array and the position of the calculated target object in the technical solution provided by the present invention;

FIG. 6 is a schematic diagram of the cross-correlation function in the technical solution provided by the present invention.

In the above figures: 1. Laser; 2. Optical shaping element; 3. Scanning mirror; 4. X-scanning motor; 5. X-scanning mirror; 6. Y-scanning motor; 7. Y-scanning mirror; 8. Field lens; 9. Underwater target object; 10. Hydrophone; 11. Host computer.

Detailed ways

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the implementations. example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

FIG. 1 is a schematic diagram of an underwater target detection system based on a laser-induced acoustic scanning method provided by the present invention. Referring to FIG. 1 , the underwater target detection system based on the laser acoustic scanning method provided in this embodiment includes: a laser 1 , an optical shaping unit 2 , a scanning galvanometer 3 , a field mirror 4 , a hydrophone 10 and a host computer 11 . Among them, the laser 1 is used as a light source to generate laser light; the optical shaping unit 2 is used to adjust the laser light generated by the laser 1; And focusing underwater, the water medium produces a photoacoustic effect, radiating sound waves to the surrounding, and the sound waves are received by the hydrophone 10 after being reflected by the underwater target object 9, and the hydrophone 10 is used to convert the received sound wave signals into electrical signals. signal, and send it to the host computer 11; the host computer 11 is connected to the laser 1 and the scanning galvanometer 3 in communication; the host computer 1 is used to control the laser output of the laser 1 and the deflection of the scanning galvanometer 3; the host computer 1 is also used to The electrical signal sent by the hydrophone 10 is adjusted to obtain an acoustic signal, and the adjusted acoustic signal is calculated and processed to obtain the depth and orientation of the underwater detected target object.

In the above system, preferably, the laser 1 is a solid pulse laser; the laser wavelength generated by the solid pulse laser is 1064 nm, the output energy is ≧ 400 mJ, the repetition frequency is 1-10 Hz, and the pulse width is 6-8 ns.

In the above system, preferably, the scanning galvanometer 3 includes: an X scanning motor 4, an X scanning mirror 5, a Y scanning motor 6 and a Y scanning mirror 7, and the X scanning motor 4 is used to drive the X scanning mirror 5 to deflect, and the Y scanning mirror The motor 6 is used to drive the Y scanning mirror 7 to deflect.

In the above system, preferably, the X scanning mirror 5 and the Y scanning mirror 7 are mirrors.

The system as described above, wherein the optical shaping unit 2 is used to adjust the laser light generated by the laser, including:

Adjust the transmission direction and beam diameter of the laser generated by the laser 1, and adjust the divergence angle of the laser beam.

For the system described above, preferably, the laser 1 is pumped by a xenon lamp to generate laser light.

FIG. 2 is a flowchart of an underwater target detection method based on a laser-induced acoustic scanning method provided by the present invention. Referring to FIG. 2 , the underwater target detection method based on the laser-induced acoustic scanning method provided in this embodiment may specifically include:

S1. The laser, the optical shaping unit, the scanning galvanometer, and the field mirror are arranged on the water platform, and the hydrophone is arranged in the water.

S2. Use a laser to generate a laser signal, and adjust the positional relationship between the laser, the optical shaping unit, the scanning galvanometer, and the field mirror, so that the laser signal generated by the laser passes through the optical shaping unit, the scanning galvanometer, and the field mirror in turn and then injects into the water. And focusing underwater, the water medium produces a photoacoustic effect and radiates sound waves to the surrounding.

S3. Adjust the position of the hydrophone in the water so that the sound wave is received by the hydrophone after being reflected by the underwater target object.

In specific applications, the upper computer can also be used to control the deflection of the scanning galvanometer, and the laser scanning method can be used to make the spot at the laser focus move in a regular shape or a specific direction in the same plane at different speeds, so that the sound waves generated on the scanning path are propagated. In the process of coherent superposition, the superimposed sound waves are reflected by the underwater target and received by the hydrophone.

S4. The hydrophone converts the received sound wave signal into an electrical signal and sends it to the upper computer.

S5, the host computer receives the electrical signal sent by the hydrophone, and adjusts the electrical signal into an acoustic signal.

S6, the upper computer processes the acoustic signal to obtain the depth and orientation of the underwater detected target object.

For example, the upper computer uses the correlation method, the difference method and the Gauss-Newton iterative algorithm to process the acoustic signal.

The following is an application example of the technical solution provided by the embodiment of the present invention.

Continuing to refer to Figure 1, the laser-induced acoustic device is installed on the waterborne airborne platform, and the hydrophone is installed on the underwater airborne platform. A high-intensity solid-state laser is used as a light source to generate laser light, and an optical shaping element is used to adjust the laser beam including the beam diameter. The high-energy-density laser is focused into the water, causing the water medium to generate thermal expansion, vaporization, dielectric breakdown and other photoacoustic effects to radiate sound waves to the surrounding. The laser focusing spot is controlled to move in a regular shape at different speeds such as sonic speed in water and supersonic speed in a scanning manner, encoding acoustic wave information for laser-induced acoustic communication. If the laser focused spot moves in a regular shape or in a specific direction at the speed of sound in water, a series of sound waves are generated on the moving path of the spot in the water medium, and the sound waves are coherently superimposed during the propagation process. During the propagation of the coherently superimposed sound waves, the underwater targets are reflected to the hydrophone installed on the underwater airborne platform, and the hydrophone is converted into an electrical signal and transmitted to the PC, and the hydrophone is demodulated by the PC to obtain the hydrophone. Under the signal reflected by the target, use the correlation method, the difference method and the Gauss-Newton iterative algorithm to process the reflected signal of the underwater target demodulated by the hydrophone, and obtain the depth and orientation of the underwater target.

If the speed of the spot is controlled so that the laser sound produces a Doppler frequency shift during the propagation process, the acoustic information of a wider spectrum can be obtained. Using this method, the information such as the spectrum of the sound source can be modulated, thereby encoding the acoustic wave signal. There are broad application prospects. FIG. 3 is a schematic diagram of a laser scanning mode in the technical solution provided by the present invention. Referring to Figure 3, it is assumed that the high-speed scanning galvanometer controls the laser focusing spot to move along the X-axis at the speed of sound in water in the X-Y plane, and the sound waves generated on the scanning path are gradually superimposed, and finally superimposed completely at the scanning end point, so that the sound waves in X It can travel farther in the direction near the axis, which greatly increases the detection range.

FIG. 4 is a schematic diagram of coherent superposition of acoustic waves in the technical solution provided by the present invention. Referring to Figure 4, the laser generates a point sound source in the water medium, if it is assumed that the sound wave generated by a single sound source propagates in the form of a spherical wave. The spherical wave expression is:

指声波在此点处的方向矢量，

指声源到此点的矢径，其中xcosα、ycosβ和zcosγ为

的方向余弦，ω为角速度，t为质点振动时间。Among them, A refers to the amplitude at one point in the sound field,

refers to the direction vector of the sound wave at this point,

Refers to the vector radius from the sound source to this point, where xcosα, ycosβ and zcosγ are

The direction cosine of , ω is the angular velocity, t is the particle vibration time.

The sound waves with the same frequency, the same vibration direction, and constant phase difference will have a stable sound intensity distribution in the superposition area.

Assuming that the sound wave generated by the sound source propagates in a certain direction, the incident wave at a point in this direction is regarded as a plane wave.

Plane wave expression: E=Acos[α-ωt]. in

Then there are two series of coherent superposition formulas for sound waves:

E=a ₁ cos(α ₁ -ωt)+a ₂ cos(α ₂ -ωt)=Acos(α-ωt),

若视a₁＝a₂＝a，α₁＝α₂，则有两个声波叠加振幅与单个声波振幅之间的关系A＝2a。in:

If a ₁ =a ₂ =a and α ₁ =α ₂ are considered, then there is a relationship A=2a between the superimposed amplitude of two acoustic waves and the amplitude of a single acoustic wave.

Assuming that when the laser spot moves along the X-axis at the speed of sound in water V _{and water} , the sound intensity of the sound wave generated by a single pulsed laser propagates on the X-axis is E ₌ a _water cos[α-ωt], then if the length of the laser spot scanning path is NL , the scanning time is t, and the laser pulse frequency is f, then there is a scanning time t=N _L /V _water , and the number of visible superimposed sound waves N≦t/f. At the end of the scan, the N sound waves start to be superimposed, that is,

E=a ₁ cos(α ₁ -ωt)+a ₂ cos(α ₂ -ωt)+...+a _N cos(α _N -ωt)=A _N cos(α-ωt), in this case, if a ₁ =a ₂ =…=a _water , α ₁ =α ₂ =…=α. Then: A _N =Na.

In order to represent the correlation between a signal x(t) and the signal y(t) after translation on the time axis, it can be represented by a correlation function, namely:

By filtering, intercepting, and finding cross-correlation of the acoustic signal collected by the hydrophone, the time τ that the acoustic wave takes to be received by the hydrophone after being reflected by the object from the sound source can be obtained.

FIG. 5 is a schematic diagram of the hydrophone array and the calculated target position in the technical solution provided by the present invention, and FIG. 6 is a schematic diagram of the cross-correlation function in the technical solution provided by the present invention. Referring to Figures 5 and 6, an array of four hydrophones can be obtained by using the differential method:

Among them, d refers to the distance of the three hydrophones A, B, and C from the coordinate origin on the coordinate axis.

Using the Gauss-Newton iterative algorithm to solve the equation system, the orientation information of the object can be obtained.

To sum up, the technical solution provided by the present utility model uses laser to generate sound source, converts laser energy into sound wave energy, uses laser scanning method, and uses sound source movement to generate Doppler effect, so that a wider sound signal can be obtained. Spectrum, which controls the speed of the laser focusing spot moving, can encode acoustic signals for laser-induced acoustic communication. The scanning galvanometer is used to make the laser form a series of sound waves on the scanning path of the spot. After the sound waves are superimposed coherently, the propagation range can be greatly increased in a specific direction, thereby expanding the detection range. It overcomes the shortcomings of high-frequency waves in water with large attenuation rate and small measurement range, and also overcomes the shortcomings of sonar sensors in traditional acoustic detection, and has the advantages of strong mobility and high sensitivity. In addition, the technical solution provided by the present utility model adopts the laser acoustic system to generate the sound source signal, and the generated acoustic signal has the advantages of high sound pressure level, wide frequency spectrum, non-contact control, etc., and the used hydrophone has a watertight structure. Good, anti-corrosion, small size, strong mobility, high sensitivity.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model, but not to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the spirit of the technical solutions of the embodiments of the present invention and range.

Claims (7)

1. an underwater target detection system based on laser-induced acoustic scanning mode, is characterized in that, comprises: laser, optical shaping unit, scanning galvanometer, field mirror, hydrophone and host computer; The laser is used as a light source to generate laser light; the optical shaping unit is used to adjust the laser light generated by the laser; The laser light generated by the laser passes through the optical shaping unit, the scanning galvanometer, and the field mirror in sequence, and then is injected into the water and focused underwater, so that the water medium produces a photoacoustic effect and radiates sound waves to the surrounding. The hydrophone is received, and the hydrophone is used to convert the received sound wave signal into an electrical signal and send it to the upper computer; The host computer is connected in communication with the laser and the scanning galvanometer; the host computer is used to control the laser output of the laser and the deflection of the scanning galvanometer; The host computer is also used to adjust the electrical signal sent by the hydrophone to obtain an acoustic signal, and to calculate and process the adjusted acoustic signal to obtain the depth and orientation of the underwater detected target object. 2. The system of claim 1, wherein the laser is a solid-state pulsed laser. 3 . The system according to claim 2 , wherein the laser wavelength generated by the solid-state pulse laser is 1064 nm, the output energy is ≧ 400 mJ, the repetition frequency is 1-10 Hz, and the pulse width is 6-8 ns. 4 . 4. The system according to claim 1, wherein the scanning galvanometer comprises: an X scanning motor, an X scanning mirror, a Y scanning motor and a Y scanning mirror, the X scanning motor is used to drive the X scanning mirror to deflect, and the Y scanning mirror The scan motor is used to drive the Y scan mirror to deflect. 5 . The system according to claim 4 , wherein the X scanning mirror and the Y scanning mirror are reflecting mirrors. 6 . 6 . The system according to claim 1 , wherein the optical shaping unit is used to adjust the transmission direction and beam diameter of the laser generated by the laser, and adjust the divergence angle of the laser beam. 7 . 7. The system according to any one of claims 1-6, wherein the laser is pumped by a xenon lamp to generate laser light.

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