CN104199048B - The remote sensing technique of streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient - Google Patents

Abstract

The remote sensing technique of streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient, the present invention relates to the remote sensing technique of measurement shallow layer sea water attenuation quotient.The present invention is to solve existing method detection efficient is relatively low and problem that can not accomplish real-time detection.First, laser instrument produces light source, launches the time-domain signal of luminous power to sea by the optical transmitting system of streak tube laser imaging radar；2nd, light reflection echo is received by receiving optics, veiling glare is filtered off by narrow band pass filter, reflected light is made to be irradiated on streak tube detector, echo light after the distortion of sea level for the streak tube detector record, and the A/D collection by streak tube laser instrument and DSP process, obtain the optical power signals of sea level echo；3rd, the attenuation quotient of shallow layer sea water is calculated using the optical power signals of sea level echo.The present invention is applied to marine exploration field.

Description

Streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient Remote sensing technique

Technical field

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

Background technology

Sea water is that oceanography field undersea detection direction needs always for attenuation quotient (or attenuation length) measurement of laser Will be in the face of the problem with solution.Current measuring method is all to be by gathering the contact type measurement such as water sample or field survey Main, its detection efficient is relatively low, and because time of measuring is longer, water quality changes it is impossible to accomplish real-time detection.

And the detection method of contactless sea water laser attenuation coefficient is by remote sensing mode, can be right in real time with large area Take remote measurement in seawater FGD process, detection efficient can be improved.Sea water to the non-contact measurement of laser attenuation coefficient due to The features such as detection efficient height, high precision, enjoys the attention of people.Especially, technique can be applied on airborne platform, its spy Survey efficiency to be greatly improved.

Content of the invention

The present invention is to solve existing method detection efficient is relatively low and problem that can not accomplish real-time detection, and provide The remote sensing technique of streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient.

The remote sensing technique of streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient presses following step Rapid realization：

First, laser instrument produces light source, by the optical transmitting system of streak tube laser imaging radar launch luminous power when Domain signal is to sea；

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

Wherein, A₀For laser instrument intrinsic light power amplitude；σ is the half of laser pulse width, and t is the time domain time of signal；

2nd, light reflection echo is received by receiving optics, filters off veiling glare by narrow band pass filter, so that reflected light is irradiated to On streak tube detector, echo light after the distortion of sea level for the streak tube detector record, and by streak tube laser instrument A/D collection and DSP process, obtain the optical power signals of sea level echo；

3rd, the attenuation quotient of shallow layer sea water is calculated using the optical power signals of sea level echo.

Invention effect：

Flash-mode laser imaging radar sea image-forming principle, the following sea water in sea can be made to echo to the back scattering of laser Become certain distortion.By to the detection of this distortion and analysis, the attenuation quotient of shallow layer sea water can be calculated.By this New method, using Matlab emulation, has detected the attenuation quotient of different quality sea water, this measurement result maximum absolute error is less than 0.01/m.The traditional method of traditional collection water sample, point-to-point measurement can be substituted using this method, be imaged by focal plane array And considerably increase shallow layer sea water attenuation quotient detection efficient using remote sensing mode.

The present invention proposes one kind and passes through sea return due to backscattering of ocean water generation using flash-mode laser imaging radar Distortion detect shallow layer sea water attenuation quotient new method.This method is to utilize streak tube laser imaging thunder by way of remote sensing Reach and face battle array detection is carried out to shallow layer sea water attenuation quotient, substantially increase detection efficient, and can accomplish that noncontact is surveyed in real time Amount.In order to more quickly and efficiently detect shallow layer sea water attenuation quotient, the present invention is based on streak tube sea laser imaging skill Art, proposes a kind of method measuring shallow layer sea water laser attenuation coefficient using the echo distortion that its back scattering under water causes.

Brief description

Fig. 1 is the optical transmitting system figure of the streak tube laser imaging radar in specific embodiment one；

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

Fig. 3 (a) is H in emulation experiment₀With attenuation quotient k₂Changing Pattern figure；

Fig. 3 (b) is P in emulation experiment₁With attenuation quotient k₂Changing Pattern figure；

Fig. 3 (c) is P in emulation experiment₂With attenuation quotient k₂Changing Pattern figure；

Fig. 3 (d) is S in emulation experiment²With attenuation quotient k₂Changing Pattern figure, work as k₂When taking 0.3/m, S²Take minima；

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

Specific embodiment

Specific embodiment one：The streak tube laser imaging radar sea return distortion measurement shallow layer sea water of present embodiment The remote sensing technique of attenuation quotient is realized according to the following steps：

First, laser instrument produces light source, by the optical transmitting system of streak tube laser imaging radar launch luminous power when Domain signal is to sea；

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

Wherein, A₀For laser instrument intrinsic light power amplitude；σ is the half of laser pulse width, and t is the time domain time of signal；

2nd, light reflection echo is received by receiving optics, filters off veiling glare by narrow band pass filter, so that reflected light is irradiated to On streak tube detector, echo light after the distortion of sea level for the streak tube detector record, and by streak tube laser instrument A/D collection and DSP process, obtain the optical power signals of sea level echo；

3rd, the attenuation quotient of shallow layer sea water is calculated using the optical power signals of sea level echo.

As shown in Figure 1 using streak tube technique of laser imaging measurement shallow layer sea water attenuation quotient experimental program.This device has Laser instrument, beam shaping, optical emission system, optical receiving system, narrow band pass filter, streak tube detector and signal processing System (A/D conversion and DSP) composition.Streak tube detector is divided into single slit and two kinds of many slits.Can be directly right using many slits Carry out face battle array detection in search coverage.Single slit streak tube detector in this way, its transmitting is wire hot spot, can be flown by carrying Device or itself sweeping are realized face battle array and are detected.

It is first turned on laser instrument, makes light source pass through to launch optics beam-expanding system, be changed into wire or hot spot is justified in face.Hot spot shines It is mapped on sea, its reflection echo is received by receiving optics.Veiling glare is filtered off by narrow band pass filter, so that reflected light is irradiated to On streak tube detector.The laser signal launched by laser instrument, streak tube detector record echo-signal, gathered by A/D, And DSP process, obtain sea level echo optical power signals.Using sea level echo optical power signals we can calculate shallow The attenuation quotient of layer sea water.

The laser of certain wavelength has certain penetration capacity for sea water, and its wave-length coverage is expressed as the laser of ocean Defeated window.Some wavelength can not penetrate ocean surface, then its seawater FGD process is considered as infinity.

Present embodiment effect：

Flash-mode laser imaging radar sea image-forming principle, the following sea water in sea can be made to echo to the back scattering of laser Become certain distortion.By to the detection of this distortion and analysis, the attenuation quotient of shallow layer sea water can be calculated.By this New method, using Matlab emulation, has detected the attenuation quotient of different quality sea water, this measurement result maximum absolute error is less than 0.01/m.The traditional method of traditional collection water sample, point-to-point measurement can be substituted using this method, be imaged by focal plane array And considerably increase shallow layer sea water attenuation quotient detection efficient using remote sensing mode.

Present embodiment proposes one kind and passes through sea return due to backscattering of ocean water using flash-mode laser imaging radar The distortion producing detects the new method of shallow layer sea water attenuation quotient.This method is to utilize streak tube laser to become by way of remote sensing As radar carries out face battle array detection to shallow layer sea water attenuation quotient, substantially increase detection efficient, and can accomplish that noncontact is real When measurement.

In order to more quickly and efficiently detect shallow layer sea water attenuation quotient, the present invention is based on streak tube sea laser Imaging technique, proposes a kind of side measuring shallow layer sea water laser attenuation coefficient using the echo distortion that its back scattering under water causes Method.

Specific embodiment two：Present embodiment from unlike specific embodiment one：Step 2 streak tube detector Echo-signal after the distortion of sea level for the record the A/D collection by streak tube laser instrument and DSP process, obtain Hai Ping The optical power signals of the echo in face are specially：

(1) streak tube detector probe unit record sea surface scattering optical power signals；

Wherein, A₁The extra large surface scattering light amplitude receiving for streak tube detector cells, t is the time domain time of signal, t₀ The time experienced from laser instrument to sea by light, k₁For atmosphere attenuation coefficien, C is the light velocity, H₀For device away from sea level height, σ is Laser pulse width half, a is scattered light power space distribution function；T₁For optical system one way transmitance, k₁For atmospheric attenuation system Number, A₀For laser instrument intrinsic light power amplitude, r is streak tube detector receiving optics radius；

(2) streak tube detector probe unit record penetrates the scattered light signal on sea level i.e. rear orientation light work(under water Rate signal；

Assume first that, under water at certain point S, laser produces back scattering, and its back scattering is by streak tube detector cells The optical power signals receiving are：

Wherein, L for the water surface to S point distance；A₂For receiving the amplitude of back scattering luminous power；N is refractive index；k₂For shallow Layer seawater FGD process；t₂The time experienced to S point from sea by laser, C_WFor laser in water medium velocity；

Its amplitude A₂It is expressed as：

Wherein, T₂Enter the transmitance of sea water for laser from air；T₃The ratio propagated along refracted light for light；T₄For Transmitance from sea water to air for the laser；B is extra large Backscattering Coefficients in Different Water Bodies, P₀Peak laser power；

Calculate laser from enter sea water travel to S point always at produce total back scattering luminous power echo-signal be：

(3) optical power signals of streak tube detector record sea level echo i.e. echo letter after the distortion of sea level Number general power is：

As can be seen from the above equation, parameters can non-be two classes, and a class is as time t, apart from H₀, seawater FGD process k₂The amount of change, in addition a class is the not amount with these three Parameters variation；

Wherein, t₀=H_0/C

Other steps and parameter are identical with specific embodiment one.

Specific embodiment three：Present embodiment from unlike specific embodiment one or two：Step 3 utilizes Hai Ping The optical power signals of face echo calculate the attenuation quotient of shallow layer sea water：

Obtained by the separation of variable：

P_t(t)=P_t(P₁,P₂,H₀,t,k₂)=P₁f(H₀,t)+P₂g(H₀,t,k₂) (8)

Wherein,

P₁=aT₁ ²P₀πr²(9)

P₂=P₀T₁ ²T₂T₃T₄b·πr²(10)

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

G′(t₁)=0 (14)

Wherein, t₁For time to peak；P_PFor peak power；E_tFor backward energy；G(t₁) actual detection signal its peak work Rate, G ' (t₁) power signal that the is actually detected derivative in the t1 moment is 0；

Therefore, P_tT () function need to meet condition (13), (14), (15)；

P₁f′(H₀,t₁)+P₂g′(H₀,t₁,k₂)=0 (16)

P₁f(H₀,t₁)+P₂g(H₀,t₁,k₂)=P_p(17)

According to equation (16)-(18) it can be deduced that：

Wherein, H₀, P₁, P₂, K₂For unknown number, obtain H by (19)-(21)₀, P₁, P₂With regard to k₂Expression formula；Obtain H₀, P₁, P₂With regard to k₂Curve；

Introduce function S², it shows as P_tThe similarity of (t) function G (t)：

S²Less, P_tT () function G (t) similarity is higher；

The H that will be drawn by equation group (19)-(21)₀, P₁, P₂With regard to k₂Changing Pattern, by these numerical value substitute into equation (22) work as S²When taking minima, obtain shallow layer sea water attenuation quotient k₂.

Wherein, t₂=L/C_w

Other steps and parameter are identical with specific embodiment one or two.

Emulation experiment：

According to theory analysis above, MATLAB is applied to verify the feasibility of present invention proposition method, with YAG laser As a example, its wavelength X=532nm.Parameters for numerical simulation is as shown in the table.

Table 1 parameters for numerical simulation list

By parameter in upper table, it is possible to obtain the echo-signal that detector receives, as shown in Figure 2.Dotted line is that echo is total Power signal, solid line is the echo-power signals that back scattering under water produces, and residual curve is the echo work(from sea surface reflection Rate signal.

Understand, the attenuation quotient that this emulation experiment is used for the sea water of calculating is 0.3/m.The algorithm being provided by the present invention, Using the signal waveform of upper figure, following result can be gone out with inverse.Fig. 3 (a) (b) (c) is respectively H₀, P₁, P₂With attenuation quotient k₂'s Changing Pattern.Fig. 3 (d) is it can be seen that work as k₂When taking 0.3/m, variance is minimum.Hence, it can be determined that the attenuation quotient of this sea water is 0.3/m.

Using the method, emulation experiment simulates the sea water of different quality respectively, and by declining obtained by this method Subtract coefficient.As shown in Figure 4.

Claims (2)

1. streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient remote sensing technique it is characterised in that It is realized according to the following steps：

First, laser instrument produces light source, launches the time domain letter of luminous power by the optical transmitting system of streak tube laser imaging radar Number arrive sea；

The time-domain signal of 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, A₀For laser instrument intrinsic light power amplitude；σ is the half of laser pulse width, and t is the time domain time of signal；

2nd, light reflection echo is received by receiving optics, filters off veiling glare by narrow band pass filter, makes reflected light be irradiated to striped On pipe detector, echo light after the distortion of sea level for the streak tube detector record, and adopted by the A/D of streak tube laser instrument Collection and DSP process, obtain the optical power signals of sea level echo；

(1) streak tube detector probe unit record sea surface scattering optical power signals；

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

$A_1=P_{0}a\frac{{\mathrm{\πr}}^2}{{\left({\mathrm{Ct}}_0\right)}^2}{T}_1^2---\left(3\right)$

Wherein, A₁The extra large surface scattering light amplitude receiving for streak tube detector cells, t is the time domain time of signal, t₀For light The time experienced from laser instrument to sea, k₁For atmosphere attenuation coefficien, C is the light velocity, H₀For device away from sea level height, σ is laser Pulsewidth half, a is scattered light power space distribution function；T₁For optical system one way transmitance, A₀For the intrinsic luminous power of laser instrument Amplitude, r is streak tube detector receiving optics radius；

(2) streak tube detector probe unit record penetrates the scattered light signal on sea level i.e. back scattering luminous power letter under water Number；

Assume first that, under water at certain point S, laser produces back scattering, its back scattering is received by streak tube detector cells To optical power signals be：

$\begin{array}{c}{P}_b\left(t,L\right)=A_2\exp \left(-\frac{{\left(t-2t_0-2t_2\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_{1}C\left(t-2t_0\right)\right)\exp \left(-2k_2{C}_W{t}_2\right)\\ \stackrel{\·}{=}{A}_2\exp \left(-\frac{{\left(t-2t_0-2t_2\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_1{H}_0\right)\exp \left(-2k_{2}L\right)\\ =A_2\exp \left(-\frac{{\left(t-2\frac{H_0}{C}-2\frac{nL}{C}\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_1{H}_0\right)\exp \left(-2k_{2}L\right)\end{array}---\left(4\right)$

Wherein, L for the water surface to S point distance；A₂For receiving the amplitude of back scattering luminous power；N is refractive index；k₂For shallow-layer sea Water fade coefficient；t₂The time experienced to S point from sea by laser, C_WFor laser in water medium velocity；

Its amplitude A₂It is expressed as：

$A_2=P_0{T}_1^2{T}_2{T}_3{T}_{4}b\frac{{\mathrm{\πr}}^2}{{(H_0+nL)}^2}---\left(5\right)$

Wherein, T₂Enter the transmitance of sea water for laser from air；T₃The ratio propagated along refracted light for light；T₄For laser Transmitance from sea water to air；B is extra large Backscattering Coefficients in Different Water Bodies, P₀Peak laser power；

Calculate laser from enter sea water travel to S point always at produce total back scattering luminous power echo-signal be：

$\begin{array}{c}{P}_b\left(t\right)=\underset{0}{\overset{+\mathrm{\∞}}{\∫}}{P}_b\left(t,L\right)dL\\ =\underset{0}{\overset{+\mathrm{\∞}}{\∫}}{P}_0{T}_1^2{T}_2{T}_3{T}_{4}b\frac{{\mathrm{\πr}}^2}{{\left(H_0+nL\right)}^2}\·\exp \left(-\frac{{\left(t-2\frac{H_0}{C}-2\frac{nL}{C}\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_1{H}_0\right)\exp \left(-2k_{2}L\right)dL\end{array}---\left(6\right)$

(3) optical power signals of streak tube detector record sea level echo i.e. echo-signal after the distortion of sea level is total Power is：

$\begin{array}{c}{P}_t\left(t\right)=P_{0}a\frac{{\mathrm{\πr}}^2}{{H_0}^2}{T}_1^2\exp \left(-\frac{{\left(t-2\frac{H_0}{C}\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_1{H}_0\right)\\ +\underset{0}{\overset{+\mathrm{\∞}}{\∫}}{P}_0{T}_1^2{T}_2{T}_3{T}_{4}b\frac{{\mathrm{\πr}}^2}{{\left(H_0+nL\right)}^2}\·\exp \left(-\frac{{\left(t-2\frac{H_0}{C}-2\frac{nL}{C}\right)}^2}{{\mathrm{\σ}}^2}\right)\exp \left(-2k_1{H}_0\right)\exp \left(-2k_{2}L\right)dL\end{array}---\left(7\right);$

3rd, the attenuation quotient of shallow layer sea water is calculated using the optical power signals of sea level echo.

2. streak tube laser imaging radar sea return distortion measurement shallow layer sea water attenuation quotient according to claim 1 Remote sensing technique is it is characterised in that step 3 calculates the attenuation quotient of shallow layer sea water using the optical power signals of sea level echo：

Obtained by the separation of variable：

P_t(t)=P_t(P₁,P₂,H₀,t,k₂)=P₁f(H₀,t)+P₂g(H₀,t,k₂) (8)

Wherein,

P₁=aT₁ ²P₀πr²(9)

P₂=P₀T₁ ²T₂T₃T₄b·πr²(10)

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

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

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

$P_p=G\left(\frac{2H_1}{C}\right)=G\left(t_1\right)---\left(13\right)$

G′(t₁)=0 (14)

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

Wherein, t₁For time to peak；P_PFor peak power；E_tFor backward energy；G(t₁) actual detection signal peak power, G ' (t₁) power signal that is actually detected is in t₁The derivative in moment is 0；

Therefore, P_tT () function need to meet condition (13), (14), (15)；

P₁f′(H₀,t₁)+P₂g′(H₀,t₁,k₂)=0 (16)

P₁f(H₀,t₁)+P₂g(H₀,t₁,k₂)=P_p(17)

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

According to equation (16)-(18) it can be deduced that：

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

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

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

Wherein, H₀, P₁, P₂, K₂For unknown number, obtain H by (19)-(21)₀, P₁, P₂With regard to k₂Expression formula；Obtain H₀, P₁, P₂Close In k₂Curve；

Introduce function S², it shows as P_tThe similarity of (t) function G (t)：

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

S²Less, P_tT () function G (t) similarity is higher；

The H that will be drawn by equation group (19)-(21)₀, P₁, P₂With regard to k₂Changing Pattern, by these numerical value substitute into equation (22) when S²When taking minima, obtain shallow layer sea water attenuation quotient k₂.