CN104199048A - Remote sensing method for measuring shallow-seawater attenuation coefficient with streak-tube laser imaging radar sea-surface echo distortion - Google Patents

Abstract

Disclosed is a remote sensing method for measuring shallow-seawater attenuation coefficient with streak-tube laser imaging radar sea-surface echo distortion with an aim to solve the problems that an existing method is low in detection effect and cannot realize real-time detection. The remote sensing method includes that 1), a laser generates light sources, time-domain signals of laser power are transmitted to the sea surface through a transmitter optical system of streak-tube imaging laser radar; 2), light reflection echo is received through a receiver optical system, stray light is filtered out through a narrow-band filter, the reflected light is irradiated on a streak-tube detector which is used for recording the echo light subjected to sea surface distortion, and after A/D (analog/digital) acquisition and DSP (digital signal processing), light power signals of the sea surface echo can be acquired; 3), calculating the attenuation coefficient of shallow seawater by the aid of the light power signals of the sea surface echo. The remote sensing method is applied to the field of sea exploration.

Description

The remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient

Technical field

The present invention relates to measure the remote sensing technique of shallow layer sea water attenuation coefficient.

Background technology

It is the problem that thalassography field undersea detection direction needs in the face of always and solves that seawater is measured for the attenuation coefficient (or attenuation length) of laser.Current measuring method is to be all main by gathering the contact type measurements such as water sample or field survey, and its detection efficiency is lower, and because Measuring Time is longer, water quality changes, and can not accomplish real-time detection.

And the detection method of contactless seawater laser attenuation coefficient is by remote sensing mode, can large area, take remote measurement for seawater attenuation coefficient in real time, can improve detection efficiency.Seawater to the non-contact measurement of laser attenuation coefficient due to detection efficiency is high, precision high enjoys people attention.Especially, technique can be applied on airborne platform, and its detection efficiency can improve greatly.

Summary of the invention

The present invention will solve the problem that existing method detection efficiency is lower and can not accomplish real-time detection, and the remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient is provided.

The remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient is realized according to the following steps:

One, laser instrument produces light source, and the time-domain signal of the optical transmitting system utilizing emitted light power by striped pipe laser imaging radar is to sea;

The time-domain signal of the luminous power that laser instrument produces is:

$P_0\left(t\right)=A_0\exp \left(\frac{t^2}{{\mathrm{\σ}}^2}\right)---\left(1\right)$

Wherein, A ₀for laser instrument intrinsic light power amplitude; σ is the half of laser pulse width, the time domain time that t is signal;

Two, light reflection echo is received by receiving optics, by narrow band pass filter elimination veiling glare, reflected light is irradiated on striped pipe detector, the echo light of striped pipe detector record after the distortion of sea level, and gather and DSP processing by the A/D of striped pipe laser instrument, obtain the optical power signals of sea level echo;

Three, utilize the optical power signals of sea level echo to calculate the attenuation coefficient of shallow layer sea water.

Invention effect:

Flash-mode laser imaging radar sea image-forming principle, the following seawater in sea causes certain distortion to the back scattering meeting of laser to echo.By the detection to this distortion and analysis, can calculate the attenuation coefficient of shallow layer sea water.By this new method, utilize Matlab emulation, survey the attenuation coefficient of different quality seawater, this measurement result maximum absolute error is less than 0.01/m.Utilize this method can substitute traditional collection water sample, the classic method of point-to-point measurement, by focal plane array imaging and utilize remote sensing mode greatly to increase shallow layer sea water attenuation coefficient detection efficiency.

The present invention proposes a kind of distortion that utilizes flash-mode laser imaging radar to produce due to backscattering of ocean water by sea echo and surveys the new method of shallow layer sea water attenuation coefficient.This method is to utilize striped pipe laser imaging radar to carry out the detection of face battle array to shallow layer sea water attenuation coefficient by the mode of remote sensing, has greatly improved detection efficiency, and can accomplish Non contact real time measurement.In order to survey more fast, efficiently shallow layer sea water attenuation coefficient, the present invention is based on striped pipe sea technique of laser imaging, a kind of method of utilizing echo distortion that its back scattering under water causes to measure shallow layer sea water laser attenuation coefficient is proposed.

Brief description of the drawings

Fig. 1 is the optical transmitting system figure of the striped pipe laser imaging radar in embodiment one;

Fig. 2 is the echo power figure that the detector in emulation experiment receives;

Fig. 3 (a) is H in emulation experiment ₀with attenuation coefficient k ₂changing Pattern figure;

Fig. 3 (b) is P in emulation experiment ₁with attenuation coefficient k ₂changing Pattern figure;

Fig. 3 (c) is P in emulation experiment ₂with attenuation coefficient k ₂changing Pattern figure;

Fig. 3 (d) is S in emulation experiment ²with attenuation coefficient k ₂changing Pattern figure, work as k ₂while getting 0.3/m, S ²get minimum value;

Fig. 4 is the attenuation coefficient numerical simulation result figure of different quality in emulation experiment.

Embodiment

Embodiment one: the remote sensing technique of the striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient of present embodiment is realized according to the following steps:

One, laser instrument produces light source, and the time-domain signal of the optical transmitting system utilizing emitted light power by striped pipe laser imaging radar is to sea;

The time-domain signal of the luminous power that laser instrument produces is:

$P_0\left(t\right)=A_0\exp \left(\frac{t^2}{{\mathrm{\σ}}^2}\right)---\left(1\right)$

Wherein, A ₀for laser instrument intrinsic light power amplitude; σ is the half of laser pulse width, the time domain time that t is signal;

Two, light reflection echo is received by receiving optics, by narrow band pass filter elimination veiling glare, reflected light is irradiated on striped pipe detector, the echo light of striped pipe detector record after the distortion of sea level, and gather and DSP processing by the A/D of striped pipe laser instrument, obtain the optical power signals of sea level echo;

Three, utilize the optical power signals of sea level echo to calculate the attenuation coefficient of shallow layer sea water.

Utilize striped pipe technique of laser imaging to measure shallow layer sea water attenuation coefficient experimental program as shown in Figure 1.This device has laser instrument, beam shaping, optical emitting system, optical receiving system, narrow band pass filter, striped pipe detector and signal processing system (A/D conversion and DSP) composition.Striped pipe detector is divided into two kinds of single slit and many slits.Utilize many slits directly to carry out the detection of face battle array for search coverage.Single slit striped pipe detector in this way, its transmitting is wire hot spot, can realize the detection of face battle array by carrying aircraft or self sweeping.

First open laser instrument, make light source pass through transmitting optics beam-expanding system, become wire or face circle hot spot.Hot spot is irradiated on sea, and its reflection echo is received by receiving optics.By narrow band pass filter elimination veiling glare, reflected light is irradiated on striped pipe detector.The laser signal of launching by laser instrument, striped pipe detector records echoed signal, gathers by A/D, and DSP processing, obtain sea level echo optical power signals.We can calculate the attenuation coefficient of shallow layer sea water to utilize sea level echo optical power signals.

The laser of certain wavelength has certain penetration capacity for seawater, and its wavelength coverage is expressed as the Laser Transmission window of ocean.Some wavelength can not penetrate ocean surface, and its seawater attenuation coefficient is considered as infinity.

Present embodiment effect:

Flash-mode laser imaging radar sea image-forming principle, the following seawater in sea causes certain distortion to the back scattering meeting of laser to echo.By the detection to this distortion and analysis, can calculate the attenuation coefficient of shallow layer sea water.By this new method, utilize Matlab emulation, survey the attenuation coefficient of different quality seawater, this measurement result maximum absolute error is less than 0.01/m.Utilize this method can substitute traditional collection water sample, the classic method of point-to-point measurement, by focal plane array imaging and utilize remote sensing mode greatly to increase shallow layer sea water attenuation coefficient detection efficiency.

The new method of shallow layer sea water attenuation coefficient is surveyed in a kind of distortion that utilizes flash-mode laser imaging radar to produce due to backscattering of ocean water by sea echo of present embodiment proposition.This method is to utilize striped pipe laser imaging radar to carry out the detection of face battle array to shallow layer sea water attenuation coefficient by the mode of remote sensing, has greatly improved detection efficiency, and can accomplish Non contact real time measurement.

In order to survey more fast, efficiently shallow layer sea water attenuation coefficient, the present invention is based on striped pipe sea technique of laser imaging, a kind of method of utilizing echo distortion that its back scattering under water causes to measure shallow layer sea water laser attenuation coefficient is proposed.

Embodiment two: present embodiment is different from embodiment one: step 2 striped pipe detector records the echoed signal after the distortion of sea level and gathers and DSP processing by the A/D of striped pipe laser instrument, and the optical power signals that obtains the echo on sea level is specially:

(1) striped pipe detector probe unit records extra large surface scattering optical power signals;

$\begin{array}{c}{P}_r\left(t\right)=A_1\exp \left(\frac{{(t-2t_0)}^2}{{\mathrm{\σ}}^2}\right)\exp (-k_1\·{2\mathrm{Ct}}_0)\\ =A_1\exp \left(\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2}\right)\exp (-k_1\·{2H}_0)\end{array}---\left(2\right)$

$A_1=P_{0}a\frac{\mathrm{\π}{r}^2}{{\left({\mathrm{Ct}}_0\right)}^2}{T_1}^2---\left(3\right)$

Wherein, A ₁for the extra large surface scattering light amplitude that striped pipe detector cells receives, the time domain time that t is signal, t ₀for the time that light experiences from laser instrument to sea, k ₁for atmospheric attenuation coefficient, C is the light velocity, H ₀for device is apart from sea level height, σ is laser pulse width half, and a is scattered light power space distribution function; T ₁for optical system one way transmitance, k ₁for atmospheric attenuation coefficient, A ₀for laser instrument intrinsic light power amplitude, r is striped pipe detector receiving optics radius;

(2) striped pipe detector probe unit record penetrates the i.e. back scattering optical power signals under water of scattered light signal on sea level;

First supposition certain 1 S place under water, laser produces back scattering, and the optical power signals that its back scattering is received by striped pipe detector cells is:

$\begin{array}{c}{P}_b=(t,L)=A_2\exp (-\frac{{(t-{2t}_0-{2t}_2)}^2}{{\mathrm{\σ}}^2})\exp (-{2k}_{1}C(t-{2t}_0))\exp (-2k_2{C}_W{t}_2)\\ \stackrel{\·}{=}{A}_2\exp (-\frac{{(t-{2t}_0-2t_2)}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\\ =A_2\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\end{array}---\left(4\right)$

Wherein, L is that the water surface is to S point distance; A ₂for receiving the amplitude of back scattering luminous power; N is refractive index; k ₂for shallow layer sea water attenuation coefficient; t ₂for the laser time that point experiences from sea to S, C _wfor laser is at water medium velocity;

Its amplitude A ₂be expressed as:

$A_2=P_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{{(H_0+\mathrm{nL})}^2}---\left(5\right)$

Wherein, T ₂the transmitance that enters seawater from air for laser; T ₃for light is along the ratio of refracted ray propagation; T ₄for the transmitance of laser from seawater to air; B is extra large Backscattering Coefficients in Different Water Bodies, P ₀laser instrument peak power;

Calculating laser propagates into the generation of S point always total back scattering luminous power echoed signal from entering seawater is:

$\begin{array}{c}{P}_b\left(t\right)=\underset{0}{\overset{+\∞}{\∫}}{P}_b(t,L)\mathrm{dL}\\ =\underset{0}{\overset{+\∞}{\∫}}{P}_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{(H_0+\mathrm{nL}{)}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}\end{array}---\left(6\right)$

(3) optical power signals that striped pipe detector records sea level echo i.e. echoed signal general power after the distortion of sea level is:

$\begin{array}{c}{P}_t\left(t\right)=P_{0}a\frac{\mathrm{\π}{r}^2}{{H_0}^2}{T_1}^2\exp (-\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\\ +\underset{0}{\overset{+\∞}{\∫}}{P}_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{(H_0+\mathrm{nL}{)}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}\end{array}---\left(7\right).$

As can be seen from the above equation, parameters can non-ly be two classes, and a class is along with time t, distance H ₀, seawater attenuation coefficient k ₂the amount changing, an other class is the amount not changing with these three parameters;

Wherein, t ₀=H _0/c

Other step and parameter are identical with embodiment one.

Embodiment three: present embodiment is different from embodiment one or two: step 3 utilizes the optical power signals of sea level echo to calculate the attenuation coefficient of shallow layer sea water:

Obtain by the separation of variable:

P _t(t)＝P _t(P ₁,P ₂,H ₀,t,k ₂)＝P ₁f(H ₀,t)+P ₂g(H ₀,t,k ₂) (8)

Wherein,

P ₁＝aT ₁ ²P ₀πr ² (9)

P ₂＝P ₀T ₁ ²T ₂T ₃T ₄b·πr ² (10)

$f(H_0,t)=\frac{1}{{H_0}^2}\exp (-\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)---\left(11\right)$

$g(H_0,t,k_2)=\underset{0}{\overset{+\∞}{\∫}}\frac{1}{{(H_0+\mathrm{nL})}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}---\left(12\right)$

Suppose in detector, the actual signal of actual detection is G (t), and this signal has following feature:

$P_p=G\left(\frac{{2H}_1}{C}\right)=G\left(t_1\right)---\left(13\right)$

G′(t ₁)＝0 (14)

$\underset{0}{\overset{\∞}{\∫}}G\left(t\right)\mathrm{dt}=E_t---\left(15\right)$

Wherein, t ₁for time to peak; P _pfor peak power; E _tfor backward energy; G (t ₁) peak power of actual detection signal, G ' (t ₁) actual detection to power signal be 0 at the derivative in t1 moment;

Therefore, P _t(t) function need satisfy condition (13), (14), (15);

P ₁f′(H ₀,t ₁)+P ₂g′(H ₀,t ₁,k ₂)＝0 (16)

P ₁f(H ₀,t ₁)+P ₂g(H ₀,t ₁,k ₂)＝P _p (17)

$P_1\underset{0}{\overset{+\∞}{\∫}}f(H_0,t)\mathrm{dt}+P_2\underset{0}{\overset{+\∞}{\∫}}g(H_0,t,k_2)\mathrm{dt}=E_t---\left(18\right)$

According to equation (16)-(18), can draw:

$\frac{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}{\underset{0}{\overset{+\∞}{\∫}}f(H_0,t)\mathrm{dt}\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·\underset{0}{\overset{+\∞}{\∫}}g(H_0,t,k_2)\mathrm{dt}}{=P}_p/E_t---\left(19\right)$

$P_1=\frac{P_p\·g^{\′}(H_0,t_1,k_2)}{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}$

$\left(20\right)$

$P_2=\frac{-P_p\·f^{\′}(H_0,t_1)}{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}---\left(21\right)$

Wherein, H ₀, P ₁, P ₂, K ₂for unknown number, obtain H by (19)-(21) ₀, P ₁, P ₂about k ₂expression formula; Obtain H ₀, P ₁, P ₂about k ₂curve;

Introduce function S ², it shows as P _t(t) similarity of function G (t):

$S^2=\underset{0}{\overset{\∞}{\∫}}{(P_{\mathrm{total}}\left(t\right)-G\left(t\right))}^2\mathrm{dt}---\left(22\right)$

S ²less, P _t(t) function G (t) similarity is higher;

Will be by the H that system of equations (19)-(21) draw ₀, P ₁, P ₂about k ₂changing Pattern, these numerical value substitution equations (22) are worked as to S ²while getting minimum value, obtain shallow layer sea water attenuation coefficient k ₂.

Wherein, t ₂=L/C _w

Other step and parameter are identical with embodiment one or two.

Emulation experiment:

According to theoretical analysis above, application MATLAB verifies the feasibility of put forward the methods of the present invention, taking YAG laser instrument as example, and its wavelength X=532nm.Parameters for numerical simulation is as shown in the table.

The list of table 1 parameters for numerical simulation

By parameter in upper table, can obtain the echoed signal that detector receives, as shown in Figure 2.Dotted line is the total power signal of echo, and solid line is the echo power signal that back scattering under water produces, and residual curve is the echo power signal from sea surface reflection.

Known, the attenuation coefficient that this emulation experiment is used for the seawater calculating is 0.3/m.By algorithm provided by the invention, utilize the signal waveform of upper figure, can go out following result by inverse.Fig. 3 (a) (b) (c) is respectively H ₀, P ₁, P ₂with attenuation coefficient k ₂changing Pattern.Fig. 3 (d) can find out and works as k ₂while getting 0.3/m, variance minimum.Therefore the attenuation coefficient that, can determine this seawater is 0.3/m.

Utilize the method, emulation experiment has been simulated respectively the seawater of different quality, and the attenuation coefficient obtaining by this method.As shown in Figure 4.

Claims (3)

1. the remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient, is characterized in that it realizes according to the following steps:

One, laser instrument produces light source, and the time-domain signal of the optical transmitting system utilizing emitted light power by striped pipe laser imaging radar is to sea;

The time-domain signal of the luminous power that laser instrument produces is:

$P_0\left(t\right)=A_0\exp \left(\frac{t^2}{{\mathrm{\σ}}^2}\right)---\left(1\right)$

Wherein, A ₀for laser instrument intrinsic light power amplitude; σ is the half of laser pulse width, the time domain time that t is signal;

Two, light reflection echo is received by receiving optics, by narrow band pass filter elimination veiling glare, reflected light is irradiated on striped pipe detector, the echo light of striped pipe detector record after the distortion of sea level, and gather and DSP processing by the A/D of striped pipe laser instrument, obtain the optical power signals of sea level echo;

Three, utilize the optical power signals of sea level echo to calculate the attenuation coefficient of shallow layer sea water.

2. the remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient according to claim 1, it is characterized in that step 2 striped pipe detector records the echoed signal after the distortion of sea level and gathers and DSP processing by the A/D of striped pipe laser instrument, the optical power signals that obtains the echo on sea level is specially:

(1) striped pipe detector probe unit records extra large surface scattering optical power signals;

$\begin{array}{c}{P}_r\left(t\right)=A_1\exp \left(\frac{{(t-2t_0)}^2}{{\mathrm{\σ}}^2}\right)\exp (-k_1\·{2\mathrm{Ct}}_0)\\ =A_1\exp \left(\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2}\right)\exp (-k_1\·{2H}_0)\end{array}---\left(2\right)$

$A_1=P_{0}a\frac{\mathrm{\π}{r}^2}{{\left({\mathrm{Ct}}_0\right)}^2}{T_1}^2---\left(3\right)$

Wherein, A ₁for the extra large surface scattering light amplitude that striped pipe detector cells receives, the time domain time that t is signal, t ₀for the time that light experiences from laser instrument to sea, k ₁for atmospheric attenuation coefficient, C is the light velocity, H ₀for device is apart from sea level height, σ is laser pulse width half, and a is scattered light power space distribution function; T ₁for optical system one way transmitance, k ₁for atmospheric attenuation coefficient, A ₀for laser instrument intrinsic light power amplitude, r is striped pipe detector receiving optics radius;

(2) striped pipe detector probe unit record penetrates the i.e. back scattering optical power signals under water of scattered light signal on sea level;

First supposition certain 1 S place under water, laser produces back scattering, and the optical power signals that its back scattering is received by striped pipe detector cells is:

$\begin{array}{c}{P}_b=(t,L)=A_2\exp (-\frac{{(t-{2t}_0-{2t}_2)}^2}{{\mathrm{\σ}}^2})\exp (-{2k}_{1}C(t-{2t}_0))\exp (-2k_2{C}_W{t}_2)\\ \stackrel{\·}{=}{A}_2\exp (-\frac{{(t-{2t}_0-2t_2)}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\\ =A_2\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\end{array}---\left(4\right)$

Wherein, L is that the water surface is to S point distance; A ₂for receiving the amplitude of back scattering luminous power; N is refractive index; k ₂for shallow layer sea water attenuation coefficient; t ₂for the laser time that point experiences from sea to S, C _wfor laser is at water medium velocity;

Its amplitude A ₂be expressed as:

$A_2=P_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{{(H_0+\mathrm{nL})}^2}---\left(5\right)$

Wherein, T ₂the transmitance that enters seawater from air for laser; T ₃for light is along the ratio of refracted ray propagation; T ₄for the transmitance of laser from seawater to air; B is extra large Backscattering Coefficients in Different Water Bodies, P ₀laser instrument peak power;

Calculating laser propagates into the generation of S point always total back scattering luminous power echoed signal from entering seawater is:

$\begin{array}{c}{P}_b\left(t\right)=\underset{0}{\overset{+\∞}{\∫}}{P}_b(t,L)\mathrm{dL}\\ =\underset{0}{\overset{+\∞}{\∫}}{P}_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{(H_0+\mathrm{nL}{)}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}\end{array}---\left(6\right)$

(3) optical power signals that striped pipe detector records sea level echo i.e. echoed signal general power after the distortion of sea level is:

$\begin{array}{c}{P}_t\left(t\right)=P_{0}a\frac{\mathrm{\π}{r}^2}{{H_0}^2}{T_1}^2\exp (-\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\\ +\underset{0}{\overset{+\∞}{\∫}}{P}_0{T_1}^2{T}_2{T}_3{T}_{4}b\frac{\mathrm{\π}{r}^2}{(H_0+\mathrm{nL}{)}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}\end{array}---\left(7\right).$

3. the remote sensing technique of striped pipe laser imaging radar sea echo distortion measurement shallow layer sea water attenuation coefficient according to claim 2, is characterized in that step 3 utilizes the optical power signals of sea level echo to calculate the attenuation coefficient of shallow layer sea water:

Obtain by the separation of variable:

P _t(t)＝P _t(P ₁,P ₂,H ₀,t,k ₂)＝P ₁f(H ₀,t)+P ₂g(H ₀,t,k ₂) (8)

Wherein,

P ₁＝aT ₁ ²P ₀πr ² (9)

P ₂＝P ₀T ₁ ²T ₂T ₃T ₄b·πr ² (10)

$f(H_0,t)=\frac{1}{{H_0}^2}\exp (-\frac{{(t-2\frac{H_0}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)---\left(11\right)$

$g(H_0,t,k_2)=\underset{0}{\overset{+\∞}{\∫}}\frac{1}{{(H_0+\mathrm{nL})}^2}\·\exp (-\frac{{(t-2\frac{H_0}{C}-2\frac{\mathrm{nL}}{C})}^2}{{\mathrm{\σ}}^2})\exp (-2k_1{H}_0)\exp (-2k_{2}L)\mathrm{dL}---\left(12\right)$

Suppose in detector, the actual signal of actual detection is G (t), and this signal has following feature:

$P_p=G\left(\frac{{2H}_1}{C}\right)=G\left(t_1\right)---\left(13\right)$

G′(t ₁)＝0 (14)

$\underset{0}{\overset{\∞}{\∫}}G\left(t\right)\mathrm{dt}=E_t---\left(15\right)$

Wherein, t ₁for time to peak; P _pfor peak power; E _tfor backward energy; G (t ₁) peak power of actual detection signal,

G ' (t ₁) power signal that arrives of actual detection is at t ₁the derivative in moment is 0;

Therefore, P _t(t) function need satisfy condition (13), (14), (15);

P ₁f′(H ₀,t ₁)+P ₂g′(H ₀,t ₁,k ₂)＝0 (16)

P ₁f(H ₀,t ₁)+P ₂g(H ₀,t ₁,k ₂)＝P _p (17)

$P_1\underset{0}{\overset{+\∞}{\∫}}f(H_0,t)\mathrm{dt}+P_2\underset{0}{\overset{+\∞}{\∫}}g(H_0,t,k_2)\mathrm{dt}=E_t---\left(18\right)$

According to equation (16)-(18), can draw:

$\frac{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}{\underset{0}{\overset{+\∞}{\∫}}f(H_0,t)\mathrm{dt}\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·\underset{0}{\overset{+\∞}{\∫}}g(H_0,t,k_2)\mathrm{dt}}{=P}_p/E_t---\left(19\right)$

$P_1=\frac{P_p\·g^{\′}(H_0,t_1,k_2)}{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}---\left(20\right)$

$P_2=\frac{-P_p\·f^{\′}(H_0,t_1)}{f(H_0,t_1)\·g^{\′}(H_0,t_1,k_2)-f^{\′}(H_0,t_1)\·g(H_0,t_1,k_2)}---\left(21\right)$

Wherein, H ₀, P ₁, P ₂, K ₂for unknown number, obtain H by (19)-(21) ₀, P ₁, P ₂about k ₂expression formula; Obtain H ₀, P ₁, P ₂about k ₂curve;

Introduce function S ², it shows as P _t(t) similarity of function G (t):

$S^2=\underset{0}{\overset{\∞}{\∫}}{(P_{\mathrm{total}}\left(t\right)-G\left(t\right))}^2\mathrm{dt}---\left(22\right)$

S ²less, P _t(t) function G (t) similarity is higher;

Will be by the H that system of equations (19)-(21) draw ₀, P ₁, P ₂about k ₂changing Pattern, these numerical value substitution equations (22) are worked as to S ²while getting minimum value, obtain shallow layer sea water attenuation coefficient k ₂.