CN104714222A - Calculation model for echo energy of laser radar system - Google Patents

Abstract

The invention relates to a calculation model for echo energy of a laser radar system. The model is based on a ray tracing method and can be applied to a coaxial or biaxial laser radar system with arbitrary laser intensity distribution and arbitrary aperture barrier for receiving the echo energy of laser received by a detector on any image surface position. The calculation model for laser echo energy provided by the invention has the advantages of high universality, high accuracy, high speed, etc.

Description

The computation model of laser radar system backward energy

Technical field

The present invention relates to laser radar technique field, particularly relate to a kind of laser radar system backward energy computation model.

Background technology

Laser radar is a kind of remote sensing equipment with high spatial and temporal resolution and measuring accuracy, is widely used in the technical fields such as unmanned navigation vehicle, three-dimension tidal current, topographic(al) reconnaissance, atmospheric exploration.Accurately calculate the return laser beam energy in pre-detection region, to the overall design of laser radar system and Performance Evaluation, there is directive significance.

1978, J.Harms proposed the return laser beam energy balane model of representative Gaussian energy distribution based on optical imaging method, and has the laser radar system of central shielding for coaxial or twin shaft; 1994, Jin Wang and Juha Kostamovaara, for the energy distribution of semiconductor laser, established return laser beam energy balane model according to the principle of spoke brightness conservation; 2005, optical imaging method expanded to again in more complicated Newtonian telescope system by the people such as Kamil Stelmaszczyk.

Summary of the invention

For background technology Problems existing, the invention provides a kind of laser radar system backward energy computation model.The present invention adopts following technical scheme:

Backward energy computation model in a kind of laser radar system, comprises the following steps:

Step 1, obtains the laser intensity Two dimensional Distribution G fallen in receiving optics visual field _{(i, j)}(X, Y, Z);

Step 2, calculating sampling point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z);

Step 3, calculating sampling point G _{(i, j)}(X, Y, Z) echo chief ray and the angle γ receiving optical axis _{(i, j)}(Z);

Step 4, calculating sampling point G _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P of detector _{(i, j)}(Z);

Step 5, calculates return laser beam gross energy P _d(Z).

In described step 1, fall into the laser intensity Two dimensional Distribution G in receiving optics visual field _{(i, j)}(X, Y, Z) is:

G _(i,j)(X,Y,Z)＝P ₀G(X,Y,Z)A _(i,j)(X,Y)

Wherein G (X, Y, Z) is any laser intensity Two dimensional Distribution, (X _d, Y _d, R _d) be the entrance pupil central coordinate of circle of receiving optics and radius, R is field of view of receiver radius, and φ receives angle of half field-of view, P ₀for incident laser peak power; Matrix A is recorded by definition n × n _{(i, j)}(X, Y) judges whether G (X, Y, Z) falls in field of view of receiver radius R: if so, then A _{(i, j)}(X, Y) is 1; Otherwise, A _{(i, j)}(X, Y) is 0.

In described step 2, sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z) acquisition methods is as follows:

If the image planes position of detector is L ', receiving optics enter window position L and radius r _wfor:

$\left\{\begin{array}{c}L=\frac{L^{\′}f}{L^{\′}-f}\\ r_w=r_d\frac{L}{L^{\′}}\end{array}\right.$

Wherein f is the focal length of receiving optics, r _dfor the radius of detector;

Enter window through sampled point G _{(i, j)}(X, Y, Z) receiving optics entrance pupil place projected outline equation φ ( _i,j) (X _w, Y _w, R _w) be:

φ _(i,j)(X _w,Y _w,R _w)＝(X _w-X _d) ²+(Y _w-Y _d) ²-R _w ²＝0

$\left\{\begin{array}{c}{X}_w=\mathrm{XL}/(L-Z)\\ Y_w=\mathrm{YL}/(L-Z)\\ R_w=r_{w}L/(L-Z)\end{array}\right.$

Wherein (X _w, Y _w, R _w) be into window projection central coordinate of circle and radius;

The entrance pupil useful area S of receiving optics _{(i, j)}(Z) be:

$\left\{\begin{array}{c}{S}_{(i,j)}\left(Z\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{B}_{(i,j)}(X,Y)}{m^2}\mathrm{\π}{R_d}^2\\ B_{(i,j)}(X,Y)=\left\{\begin{array}{c}{(X-X_d)}^2+{(Y-Y_d)}^2\≤R_d^2\\ {(X-X_w)}^2+{(Y-Y_w)}^2\≤R_w^2\\ 1,{(X-X_s)}^2+{(Y-Y_s)}^2\≥R_s^2\\ {(X-X_d)}^2+{(Y-Y_d)}^2\≥R_d^{\′2}\\ ...\\ 0\end{array}\right.\end{array}\right.$

S _{(i, j)}(Z) for after removing the circular shield portions of center and peripheral, the overlapping area of window projection and entrance pupil is entered; Wherein (X _d, Y _d, R ' _d) centered by the central coordinate of circle of shield portions and radius, (X _s, Y _s, R _s) be the central coordinate of circle of edge shield portions and radius; Matrix B is recorded by definition m × m _{(i, j)}(X, Y) aided solving, if B _{(i, j)}(X, Y) is at entrance pupil useful area S _{(i, j)}(Z) in, then B _{(i, j)}(X, Y) is 1; Otherwise, B _{(i, j)}(X, Y) is 0;

Sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z) be:

${\mathrm{\ψ}}_{(i,j)}\left(Z\right)=\frac{S_{(i,j)}\left(Z\right)}{Z^2}.$

In described step 3, sampled point G _{(i, j)}(X, Y, Z) echo chief ray and the angle γ receiving optical axis _{(i, j)}(Z) be:

${\mathrm{\γ}}_{(i,j)}\left(Z\right)={\tan }^{-1}\left[\frac{\sqrt{{(X-X_d)}^2+{(Y-Y_d)}^2}}{Z}\right].$

In described step 4, sampled point G _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P of detector _{(i, j)}(Z) be:

$P_{(i,j)}\left(Z\right)=\frac{G_{(i,j)}(X,Y,Z)\cos {\mathrm{\γ}}_{(i,j)}\left(Z\right){\mathrm{\ψ}}_{(i,j)}\left(Z\right)}{\mathrm{\π}}\mathrm{\ϵ}{\mathrm{\τ}}^2{\mathrm{\η}}_1{\mathrm{\η}}_2\cos \mathrm{\θ}.$

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η ₁for the transmissivity of optical transmitting system, η ₂for the transmissivity of receiving optics, θ is the angle launching optical axis and target face normal.

In described step 5, return laser beam gross energy P _d(Z) be:

P _d(Z)＝ΣΣP _(i,j)(Z)。

Described any incident laser intensity Two dimensional Distribution G (X, Y, Z) describes by analytic expression, or surveys real LASER Light Source to obtain by equipment such as CCD camera.

Described entrance pupil useful area S _{(i, j)}(Z) computing method are applicable to unobstructed, or many places are blocked and the irregular receiving optics of occlusion shapes.

By changing the image planes position L ' of detector, obtain the return laser beam energy P that detector receives _d(Z).

Compared with prior art, the present invention proposes a kind of more accurately, have more the return laser beam energy balane model of universality.This model, based on ray tracing method, can be used for the light source of any Distribution of laser intensity, both can have been described by analytic expression and also can have been obtained by actual measurement; This model can be used for the receiving optics of blocking arbitrarily position, arbitrarily occlusion shapes; This model can also obtain the return laser beam energy that detector receives in any image planes position place, is beneficial to and obtains better energy response by focusing to detector position.

The research of laser radar is still in the starting stage at home, and similar research work rarely has report, and the present invention compensate for the blank of this technical field.

Accompanying drawing explanation

Fig. 1 two-axis laser radar system Organization Chart;

The position relationship schematic diagram of Fig. 2 incident laser and field of view of receiver;

Fig. 3 return laser beam energy arithmetic schematic diagram;

There is the reception entrance pupil aperture schematic diagram that center and peripheral circle is blocked in Fig. 4;

There is the reception entrance pupil aperture schematic diagram that edge rectangle blocks in Fig. 5;

Gaussian laser beam intensity distributions in Fig. 6 example 1;

In Fig. 7 example 1, return laser beam energy is with the changing trend diagram of detection range;

Flat-top laser beam intensity distribution in Fig. 8 example 2;

In Fig. 9 example 2, return laser beam energy is with the changing trend diagram of detection range;

Semiconductor laser intensity distributions is surveyed in Figure 10 example 3;

In Figure 11 example 3, return laser beam energy is with the changing trend diagram of detection range.

Embodiment

Now by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is further explained.

Fig. 1 is two-axis laser radar system Organization Chart (if coaxial framework, then d is 0).In order to accurately calculate the return laser beam energy at different detection range place, need to consider 3 key factors:

1. in biaxial system, the existence due to overlap factor makes closely, the incoming laser beam at middle distance place cannot fall in field of view of receiver completely, and the interval inner laser backward energy of this detection range is partly utilized;

2. detector is placed in receiving optics focal plane place usually, detects the target of distant location, and the focal length by detector size and receiving optics limits, and causes return laser beam energy that is near, middle distance place to lose by defocusing effect affects;

3. more complicated receiving optics generally blocks existence, affects to return laser beam energy.

By the method for ray tracing, first needing the laser intensity to being incident to target face to sample, obtaining the laser intensity Two dimensional Distribution G fallen in field of view of receiver _{(i, j)}(X, Y, Z), and be considered as effective sampling points; Secondly, each effective sampling points G is calculated _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P on detector _{(i, j)}, and carry out suing for peace to obtain gross energy P (Z) _d(Z).

Fig. 2 is the position relationship schematic diagram of incident laser and field of view of receiver, and wherein dark-shaded part represents and falls into field of view of receiver inner laser energy, its intensity Two dimensional Distribution G _{(i, j)}(X, Y, Z) is:

G _(i,j)(X,Y,Z)＝P ₀G(X,Y,Z)A _(i,j)(X,Y)

Wherein G (X, Y, Z) is any laser intensity Two dimensional Distribution, (X _d, Y _d, R _d) be the entrance pupil central coordinate of circle of receiving optics and radius, R is field of view of receiver radius, and φ receives angle of half field-of view, P ₀for incident laser peak power.Matrix A is recorded by definition n × n _{(i, j)}(X, Y) judges whether G (X, Y, Z) falls in field of view of receiver radius R: if so, then A _{(i, j)}(X, Y) is 1; Otherwise, A _{(i, j)}(X, Y) is 0.

G (X, Y, Z) can be described by analytic expression, and for standard gaussian light beam, its intensity Two dimensional Distribution is:

$G(X,Y,Z)=\frac{C_0}{{\mathrm{\ω}}_0^2+{\left(Z\tan \mathrm{\δ}\right)}^2}\exp {(-\frac{{[X-d-Z\tan \left(\mathrm{\Δ\υ}\right)]}^2+Y^2}{{\mathrm{\ω}}_0^2+{\left(Z\tan \mathrm{\δ}\right)}^2})}^{1/2}---\left(2\right)$

Wherein ω ₀for waist radius, λ is wavelength, and δ is laser-beam divergence half-angle, and d launches optical axis and the distance (in coaxial system, d is 0) receiving optical axis, and Δ υ is the angle launched optical axis and receive between optical axis, C ₀be constant and meet:

$C_0{\∫}_{-\∞}^{\∞}{\∫}_{-\∞}^{\∞}G(X,Y,Z)\mathrm{dxdy}=P_0---\left(3\right)$

Formula (3) makes the gross energy of incoming laser beam be normalized into steady state value, does not change with detection range.

For eliminating the difference of perfect light source and real light sources and the error of calculation introduced, G (X, Y, Z) can also survey real LASER Light Source to obtain by equipment such as CCD camera.

Fig. 3 is expressed as return laser beam energy arithmetic schematic diagram, and receiving optics complicated arbitrarily in figure can be equivalent to thin lens, and its aperture is entrance pupil (optical aberration is ignored); Detector is positioned near lens focal plane, its object space become real image for entering window.

Effective sampling points G _{(i, j)}the return laser beam energy demand that (X, Y, Z) reflexes to detector is by the entrance pupil of receiving optics and enter window, and as the shade envelope part in Fig. 3, it represents sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) return laser beam light beam _{(i, j)}(Z), be entrance pupil and enter window and correspond respectively to sampled point G _{(i, j)}the common factor of the solid angle of (X, Y, Z).From projection relation, ψ _{(i, j)}(Z) be entrance pupil useful area S _{(i, j)}(Z) with detection range Z square ratio, wherein entrance pupil useful area S _{(i, j)}(Z) for outside removing aperture blocking part, window is entered through sampled point G _{(i, j)}(X, Y, Z) projection at entrance pupil place and the overlapping area of entrance pupil.

If the image planes position of detector is L ', detector is into window through receiving optics in object space imaging, then enter window position L and radius r _wfor:

$\left\{\begin{array}{c}L=\frac{L^{\′}f}{L^{\′}-f}\\ r_w=r_d\frac{L}{L^{\′}}\end{array}\right.---\left(4\right)$

Wherein f is the focal length of receiving optics, r _dfor the radius of detector.

Enter window through sampled point G _{(i, j)}(X, Y, Z) receiving optics entrance pupil place projected outline equation φ ( _i,j) (X _w, Y _w, R _w) be:

φ _(i,j)(X _w,Y _w,R _w)＝(X _w-X _d) ²+(Y _w-Y _d) ²-R _w ²＝0

$\left\{\begin{array}{c}{X}_w=\mathrm{XL}/(L-Z)\\ Y_w=\mathrm{YL}/(L-Z)\\ R_w=r_{w}L/(L-Z)\end{array}\right.---\left(5\right)$

Wherein (X _w, Y _w, R _w) be into window projection central coordinate of circle and radius;

Fig. 4 is expressed as the reception entrance pupil aperture schematic diagram existing and block, and block there is center and peripheral circle, wherein dark-shaded part is entrance pupil useful area S _{(i, j)}(Z):

Wherein (X _d, Y _d, R ' _d) centered by the central coordinate of circle of shield portions and radius, wherein (X _s, Y _s, R _s) be the central coordinate of circle of edge shield portions and radius; Matrix B is recorded by definition m × m _{(i, j)}(X, Y) aided solving, if B _{(i, j)}(X, Y) is at entrance pupil useful area S _{(i, j)}(Z) in, then B _{(i, j)}(X, Y) is 1; Otherwise, B _{(i, j)}(X, Y) is 0.

Receive entrance pupil useful area S _{(i, j)}(Z) computing method can be used for existing the situation that edge rectangle blocks equally, as shown in Figure 5, and its entrance pupil useful area S _{(i, j)}(Z) be:

$\left\{\begin{array}{c}{S}_{(i,j)}\left(Z\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{B}_{(i,j)}(X,Y)}{m^2}\mathrm{\π}{R_d}^2\\ B_{(i,j)}(X,Y)=\left\{\begin{array}{c}{(X-X_d)}^2+{(Y-Y_d)}^2\≤R_d^2\\ 1,{(X-X_w)}^2+{(Y-Y_w)}^2\≤R_w^2\\ X\≤X_s\\ 0\end{array}\right.\end{array}\right.---\left(7\right)$

Sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z) be:

${\mathrm{\ψ}}_{(i,j)}\left(Z\right)=\frac{S_{(i,j)}\left(Z\right)}{Z^2}---\left(8\right)$

By the constraint of application conditions, receiving optics version is different.In overlength distance detection purposes, receiving optics adopts autocollimator structure usually, and the existence of secondary mirror will cause central shielding; In order to reduce the detection blind area effective control system size closely located, there is certain overlap between the launching and receiving aperture of two-axis laser radar, edge will be caused to block.

If the detection of a target is considered as lambertian, point source is relevant with surface normal direction with this direction to the radiant quantity in solid angle in prescribed direction in space, therefore needs in fig. 2 to consider sampled point G _{(i, j)}(X, Y, Z) echo chief ray and the angle γ receiving optical axis _{(i, j)}(Z):

${\mathrm{\γ}}_{(i,j)}\left(Z\right){=\tan }^{-1}\left[\frac{\sqrt{{(X-X_d)}^2+{(Y-Y_d)}^2}}{Z}\right]---\left(9\right)$

Obtained by formula (1), (7) and (8), sampled point G _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P of detector _{(i, j)}(Z) be:

$P_{(i,j)}\left(Z\right)=\frac{G_{(i,j)}(X,Y,Z)\cos {\mathrm{\γ}}_{(i,j)}\left(Z\right){\mathrm{\ψ}}_{(i,j)}\left(Z\right)}{\mathrm{\π}}\mathrm{\ϵ}{\mathrm{\τ}}^2{\mathrm{\η}}_1{\mathrm{\η}}_2\cos \mathrm{\θ}---\left(10\right)$

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η ₁for the transmissivity of optical transmitting system, η ₂for the transmissivity of receiving optics, θ is the angle launching optical axis and target face normal.

To falling into whole effective sampling points G in field of view of receiver _{(i, j)}the return laser beam energy P of (X, Y, Z) _{(i, j)}(Z) sue for peace, obtain the return laser beam gross energy P at detection range Z place _d(Z) be:

P _d(Z)＝ΣP _(i,j)(Z) (11)

In overlength distance detection purposes, often detector is placed in the focal plane place of receiving optics, the target for infinite distance carries out detecting (entering window position in infinite distance); And in short distance detection purposes, need the image planes position by adjusting detector, to carry out detecting (entering window position at limited distance place) for limited target far away.Therefore, by changing the image planes position L ' of detector in formula (4), the return laser beam energy P that detector receives in any image planes position place is obtained _d(Z), contribute to realizing best return laser beam energy response.

Specific embodiment

By three examples, feasibility of the present invention is described.Suppose that one way atmospheric transmissivity τ is 0.98, target reflectivity ε is 0.1, the transmissivity η of optical transmitting system ₁be 0.9, the transmissivity η of receiving optics ₂be 0.85, the angle theta of launching optical axis and target face normal is 0 °.Utilize 3 examples of above-mentioned return laser beam energy balane model in table 1, its optical parametric is:

Table 1

Embodiment 1:

Fig. 6 is Gaussian laser beam intensity distributions in example 1, Fig. 7 be in example 1 return laser beam energy with the changing trend diagram of detection range.

In Fig. 7, the return laser beam energy at 1m place is 5.71 × 10 ^-6the return laser beam energy at W, 150m place is 9.79 × 10 ^-8w, 7m place return laser beam energy reaches maximal value 2.09 × 10 ^-5the dynamic range of W, 1m to 150m detection range inner laser backward energy about 213 times.

Embodiment 2:

Fig. 8 be in example 2 flat-top laser beam intensity distribution, Fig. 9 be in example 2 return laser beam energy with the changing trend diagram of detection range.

In Fig. 9, the return laser beam energy at 5m place is 1.5 × 10 ^-5the return laser beam energy at W, 500m place is 1.39 × 10 ^-7w, 10m place return laser beam energy reaches maximal value 1.53 × 10 ^-5the dynamic range of W, 5m to 500m detection range inner laser backward energy about 110 times.

Embodiment 3:

Figure 10 surveys semiconductor laser intensity distributions in example 3, Figure 11 be in example 3 return laser beam energy with the changing trend diagram of detection range.

In Figure 11, the return laser beam energy at 1m place is 5.29 × 10 ^-6the return laser beam energy at W, 150m place is 9.8 × 10 ^-8w, 7m place return laser beam energy reaches maximal value 6.5 × 10 ^-6the dynamic range of W, 1m to 150m detection range inner laser backward energy about 66.4 times.

Describe by 3 examples the coaxial or two-axis laser radar system that laser radar echo energy balane model that the present invention proposes can be used for any Distribution of laser intensity, arbitrarily aperture blocking, obtain the return laser beam energy that detector receives in any image planes position place.Under it is emphasized that above-mentioned 3 calculated examples are all based upon the conditions such as same reflection characteristic goal thing, atmospheric transmissivity, optical system transmissivity, in the application of reality, consider the variability of above-mentioned parameter, return laser beam energy will change.

Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improve and convert the protection domain that all should belong to claims of the present invention.

Claims (9)

1. a backward energy computation model in laser radar system, is characterized in that, comprise the following steps:

Step 1, obtains the laser intensity Two dimensional Distribution G fallen in receiving optics visual field _{(i, j)}(X, Y, Z);

Step 2, calculating sampling point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z);

Step 3, calculating sampling point G _{(i, j)}(X, Y, Z) echo chief ray and the angle γ receiving optical axis _{(i, j)}(Z);

Step 4, calculating sampling point G _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P of detector _{(i, j)}(Z);

Step 5, calculates return laser beam gross energy P _d(Z).

2. laser radar system backward energy computation model according to claim 1, is characterized in that, in described step 1, falls into the laser intensity Two dimensional Distribution G in receiving optics visual field _{(i, j)}(X, Y, Z) is:

G _(i,j)(X,Y,Z)＝P ₀G(X,Y,Z)A _(i,j)(X,Y)

Wherein, G (X, Y, Z) is any laser intensity Two dimensional Distribution, (X _d, Y _d, R _d) be the entrance pupil central coordinate of circle of receiving optics and radius, R is field of view of receiver radius, receive angle of half field-of view, P ₀for incident laser peak power; Matrix A is recorded by definition n × n _{(i, j)}(X, Y) judges whether G (X, Y, Z) falls in field of view of receiver radius R: if so, then A _{(i, j)}(X, Y) is 1; Otherwise, A _{(i, j)}(X, Y) is 0.

3. laser radar system backward energy computation model according to claim 1, is characterized in that, in described step 2, and sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z) acquisition methods is as follows:

If the image planes position of detector is L ', receiving optics enter window position L and radius r _wfor:

$\left\{\begin{array}{c}L=\frac{L^{\′}f}{L^{\′}-f}\\ r_w=r_d\frac{L}{L^{\′}}\end{array}\right.$

Wherein f is the focal length of receiving optics, r _dfor the radius of detector;

Enter window through sampled point G _{(i, j)}(X, Y, Z) receiving optics entrance pupil place projected outline equation φ ( _i,j) (X _w, Y _w, R _w) be:

φ _(i,j)(X _w,Y _w,R _w)＝(X _w-X _d) ²+(Y _w-Y _d) ²-R _w ²＝0

$\left\{\begin{array}{c}{X}_w=\mathrm{XL}/(L-Z)\\ Y_w=\mathrm{YL}/(L-Z)\\ R_w=r_{w}L/(L-Z)\end{array}\right.$

Wherein (X _w, Y _w, R _w) be into window projection central coordinate of circle and radius;

The entrance pupil useful area S of receiving optics _{(i, j)}(Z) be:

$\left\{\begin{array}{c}{S}_{(i,j)}\left(Z\right)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{B}_{(i,j)}(X,Y)}{m^2}{{\mathrm{\πR}}_d}^2\\ B_{(i,j)}(X,Y)=\left\{\begin{array}{c}{(X-X_d)}^2+{(Y-Y_d)}^2\≤R_d^2\\ {(X-X_w)}^2+{(Y-Y_w)}^2\≤R_w^2\\ 1,{(X-X_s)}^2+{(Y-Y_s)}^2\≥R_s^2\\ {(X-X_s)}^2+{(Y-Y_d)}^2\≥R_d^{\′2}\\ ...\\ 0\end{array}\right.\end{array}\right.$

S _{(i, j)}(Z) for after removing the circular shield portions of center and peripheral, the overlapping area of window projection and entrance pupil is entered, wherein (X _d, Y _d, R ' _d) centered by the central coordinate of circle of shield portions and radius, (X _s, Y _s, R _s) be the central coordinate of circle of edge shield portions and radius, record matrix B by definition m × m _{(i, j)}(X, Y) aided solving, if B _{(i, j)}(X, Y) is at entrance pupil useful area S _{(i, j)}(Z) in, then B _{(i, j)}(X, Y) is 1; Otherwise, B _{(i, j)}(X, Y) is 0,

Sampled point G _{(i, j)}effective solid angle ψ of (X, Y, Z) echo beam _{(i, j)}(Z) be:

${\mathrm{\ψ}}_{(i,j)}\left(Z\right)=\frac{S_{(i,j)}\left(Z\right)}{Z^2}.$

4. laser radar system backward energy computation model according to claim 1, is characterized in that, in described step 3, and sampled point G _{(i, j)}(X, Y, Z) echo chief ray and the angle γ receiving optical axis _{(i, j)}(Z) be:

${\mathrm{\γ}}_{(i,j)}\left(Z\right)={\tan }^{-1}\left[\frac{\sqrt{{(X-X_d)}^2+{(Y-Y_d)}^2}}{Z}\right].$

5. laser radar system backward energy computation model according to claim 1, is characterized in that, in described step 4, and sampled point G _{(i, j)}(X, Y, Z) reflexes to the return laser beam energy P of detector _{(i, j)}(Z) be:

$P_{(i,j)}\left(Z\right)=\frac{G_{(i,j)}(X,Y,Z)\cos {\mathrm{\γ}}_{(i,j)}\left(Z\right){\mathrm{\ψ}}_{(i,j)}\left(Z\right)}{\mathrm{\π}}{\mathrm{\ϵ\τ}}^2{\mathrm{\η}}_1{\mathrm{\η}}_2\cos \mathrm{\θ}$

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η ₁for the transmissivity of optical transmitting system, η ₂for the transmissivity of receiving optics, θ is the angle launching optical axis and target face normal.

6. laser radar system backward energy computation model according to claim 1, is characterized in that, in described step 5, and return laser beam gross energy P _d(Z) be:

P _d(Z)＝ΣΣP _(i,j)(Z)。

7. laser radar system backward energy computation model according to claim 2, it is characterized in that, described any incident laser intensity Two dimensional Distribution G (X, Y, Z) described by analytic expression, or survey real LASER Light Source to obtain by CCD camera.

8. laser radar system backward energy computation model according to claim 3, is characterized in that, described entrance pupil useful area S _{(i, j)}(Z) computing method are applicable to unobstructed, or many places are blocked and the irregular receiving optics of occlusion shapes.

9. laser radar system backward energy computation model according to claim 3, is characterized in that, by changing the image planes position L ' of detector, obtains the return laser beam energy P that detector receives _d(Z).