CN104714222B - The computational methods of laser radar system backward energy - Google Patents

Abstract

The present invention relates to a kind of computation model of laser radar system backward energy.This model is based on ray tracing method, available for any Distribution of laser intensity, the coaxial or two-axis laser radar system of any aperture blocking, obtains the return laser beam energy that detector is received at any image planes position.Return laser beam energy balane model proposed by the present invention has the features such as universality is strong, precision is high, speed is fast.

Description

The computational methods of laser radar system backward energy

Technical field

The present invention relates to laser radar technique field, more particularly to a kind of laser radar system backward energy computational methods.

Background technology

Laser radar is a kind of remote sensing equipment with high spatial and temporal resolution and measurement accuracy, is widely used in nobody and leads The technical fields such as boat car, three-dimension tidal current, topographic(al) reconnaissance, Atmospheric Survey.The laser accurately calculated in pre-detection region is returned Wave energy, has directive significance to the overall design and Performance Evaluation of laser radar system.

1978, J.Harms proposed the return laser beam energy meter of representative Gaussian Energy distribution based on optical imaging method Model is calculated, and is used for the laser radar system that coaxial or twin shaft has central shielding；, Jin Wang and Juha in 1994 Kostamovaara is directed to the Energy distribution of semiconductor laser, and return laser beam energy is established according to the principle of spoke brightness conservation Computation model；2005, optical imaging method was expanded to more complicated newton again and looked in the distance by Kamil Stelmaszczyk et al. In mirror system.

The content of the invention

The problem of existing for background technology, the present invention provides a kind of laser radar system backward energy computational methods.This Invention is adopted the following technical scheme that：

Backward energy computational methods, comprise the following steps in a kind of laser radar system：

Step 1, the laser intensity Two dimensional Distribution G fallen into receiving optics visual field is obtained_(i,j)(X,Y,Z)；

Step 2, sampled point G is calculated_(i,j)Effective solid angle ψ of (X, Y, Z) echo beam_(i,j)(Z)；

Step 3, sampled point G is calculated_(i,j)(X, Y, Z) echo chief ray and the angle γ for receiving optical axis_(i,j)(Z)；

Step 4, sampled point G is calculated_(i,j)(X, Y, Z) reflexes to the return laser beam energy P of detector_(i,j)(Z)；

Step 5, return laser beam gross energy P is calculated_d(Z)。

In the step 1, the laser intensity Two dimensional Distribution G fallen into receiving optics visual field_(i,j)(X, Y, Z) is：

G_(i,j)(X, Y, Z)=P₀G(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 receiving optics the entrance pupil center of circle Coordinate and radius, R are field of view of receiver radius,Receive angle of half field-of view, P₀For incident laser peak power；By defining n × n notes Record matrix A_(i,j)(X, Y) judges whether G (X, Y, Z) is fallen into 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 the step 2, sampled point G_(i,j)Effective solid angle ψ of (X, Y, Z) echo beam_(i,j)(Z) acquisition methods are such as Under：

If the image planes position of detector is L ', receiving optics enters window position L and radius r_wFor：

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

Enter the sampled point G of window_(i,j)(X, Y, Z) at receiving optics entrance pupil 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

Wherein (X_w,Y_w,R_w) it is the central coordinate of circle and radius projected into window；

The entrance pupil effective area S of receiving optics_(i,j)(Z) it is：

S_(i,j)(Z) to remove after the circular shield portions of center and peripheral, window projection and the overlapping area of entrance pupil are entered；Wherein (X_d,Y_d,R′_d) centered on shield portions central coordinate of circle and radius, (X_s,Y_s,R_s) for edge shield portions central coordinate of circle and Radius；Matrix B is recorded by defining m × m_(i,j)(X, Y) auxiliary is calculated, if B_(i,j)(X, Y) is in entrance pupil effective area S_(i,j)(Z) It is interior, 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) it is：

In the step 3, sampled point G_(i,j)(X, Y, Z) echo chief ray and the angle γ for receiving optical axis_(i,j)(Z) it is：

In the step 4, sampled point G_(i,j)(X, Y, Z) reflexes to the return laser beam energy P of detector_(i,j)(Z) it is：

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η₁For the transmissivity of optical transmitting system, η₂To receive The transmissivity of optical system, θ is transmitting optical axis and the angle of target face normal.

In the step 5, return laser beam gross energy P_d(Z) it is：

P_d(Z)=∑ ∑ P_(i,j)(Z)。

Described any incident laser intensity Two dimensional Distribution G (X, Y, Z) can be described by analytic expression, or pass through CCD phases The equipment such as machine survey real LASER Light Source to obtain.

Described entrance pupil effective area S_(i,j)(Z) computational methods are applied to unobstructed, or many places block and occlusion shapes Irregular receiving optics.

By changing the image planes position L ' of detector, the return laser beam energy P that detector is received is obtained_d(Z)。

Compared with prior art, the present invention proposes a kind of more accurate, more universality return laser beam energy balane mould Type.The model is based on ray tracing method, available for the light source of any Distribution of laser intensity, can both be described by analytic expression It can also be obtained by surveying；The model can be used for any blocking position, the receiving optics of any occlusion shapes；The model The return laser beam energy that detector is received at any image planes position can also be obtained, beneficial to by being carried out to detector position Focus to obtain more preferably energy response.

The research of laser radar is still in the starting stage at home, and similar research work is rarely reported, and the present invention makes up The blank of the technical field.

Brief description of the drawings

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

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

Fig. 3 return laser beam energy arithmetic schematic diagrams；

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 is blocked in Fig. 5；

Gaussian laser beam intensity distribution in Fig. 6 examples 1；

In Fig. 7 examples 1 return laser beam energy with detection range changing trend diagram；

Flat-top laser beam intensity is distributed in Fig. 8 examples 2；

In Fig. 9 examples 2 return laser beam energy with detection range changing trend diagram；

Semiconductor laser intensity distribution is surveyed in Figure 10 examples 3；

In Figure 11 examples 3 return laser beam energy with detection range changing trend diagram.

Embodiment

Now by embodiment, and with reference to accompanying drawing, technical scheme is further explained.

Fig. 1 is that (if coaxial framework, 0) d is to two-axis laser radar system Organization Chart.In order to accurately calculate different detections Return laser beam energy at distance is, it is necessary in view of 3 key factors：

1. in biaxial system, because the presence of overlap factor make it that the incoming laser beam near, middle distance can not be complete Fall into field of view of receiver so that return laser beam energy is partly utilized in the detection range is interval；

2. detector is usually placed in receiving optics focal plane, the target to distant location is detected, and is detected The focal length limitation of device size and receiving optics, cause return laser beam energy near, middle distance influenceed by defocusing effect and Loss；

3. more complicated receiving optics typically blocks presence, return laser beam energy is affected.

Pass through the method for ray tracing, it is necessary first to the laser intensity for being incident to target face is sampled, acquisition is fallen into Laser intensity Two dimensional Distribution G in field of view of receiver_(i,j)(X, Y, Z), and it is considered as effective sampling points；Secondly, calculating is each effectively adopted Sampling point G_(i,j)The return laser beam energy P that (X, Y, Z) is reflexed on detector_(i,j)(Z), and summed to obtain gross energy P_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 to fall into reception Laser energy in visual field, its intensity Two dimensional Distribution G_(i,j)(X, Y, Z) is：

G_(i,j)(X, Y, Z)=P₀G(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 receiving optics the entrance pupil center of circle Coordinate and radius, R are field of view of receiver radius,Receive angle of half field-of view, P₀For incident laser peak power.By defining n × n notes Record matrix A_(i,j)(X, Y) judges whether G (X, Y, Z) is fallen into 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, by taking standard gaussian light beam as an example, and its intensity Two dimensional Distribution is：

Wherein ω₀For waist radius, λ is wavelength, and δ is laser-beam divergence half-angle, d for transmitting optical axis with receive optical axis away from From (d is 0 in coaxial system), Δ υ is transmitting optical axis and receives the angle between optical axis, C₀It is constant and satisfaction：

Formula (3) causes the gross energy of incoming laser beam to be normalized into steady state value, is not changed with detection range.

To eliminate the calculation error that the difference of perfect light source and real light sources is introduced, G (X, Y, Z) can also pass through CCD The equipment such as camera survey real LASER Light Source to obtain.

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

Effective sampling points G_(i,j)The return laser beam energy demand that (X, Y, Z) reflexes to detector passes through receiving optics Entrance pupil and enter the shade envelope part in window, such as Fig. 3, it represents sampled point G_(i,j)The effective of (X, Y, Z) return laser beam light beam stands Body angle ψ_(i,j)(Z), as entrance pupil corresponds respectively to sampled point G with entering window_(i,j)The common factor of the solid angle of (X, Y, Z).Closed by projection Knowable to system, ψ_(i,j)(Z) it is entrance pupil effective area S_(i,j)(Z) with detection range Z square the ratio between, wherein entrance pupil effective area S_(i,j)(Z) to remove outside aperture blocking part, the sampled point G of window is entered_(i,j)The weight of the projection and entrance pupil of (X, Y, Z) at entrance pupil Folded area.

If the image planes position of detector is L ', the received optical system of detector is into window, then in object space imaging Enter window position L and radius r_wFor：

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

Enter the sampled point G of window_(i,j)(X, Y, Z) at receiving optics entrance pupil 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

Wherein (X_w,Y_w,R_w) it is the central coordinate of circle and radius projected into window；

Fig. 4 is expressed as the presence of the reception entrance pupil aperture schematic diagram blocked, exemplified by it there is center and peripheral circle and block, its Middle dark-shaded part is entrance pupil effective area S_(i,j)(Z)：

Wherein (X_d,Y_d,R′_d) centered on shield portions central coordinate of circle and radius, wherein (X_s,Y_s,R_s) blocked for edge Partial central coordinate of circle and radius；Matrix B is recorded by defining m × m_(i,j)(X, Y) auxiliary is calculated, if B_(i,j)(X, Y) is in entrance pupil Effective 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 effective area S_(i,j)(Z) computational methods are equally applicable to there is a situation where that edge rectangle is blocked, such as Shown in Fig. 5, its entrance pupil effective area S_(i,j)(Z) it is：

Sampled point G_(i,j)Effective solid angle ψ of (X, Y, Z) echo beam_(i,j)(Z) it is：

Constrained by application conditions, receiving optics structure type is different.In overlength distance detection purposes, light is received System generally uses autocollimator structure, and the presence of secondary mirror will cause central shielding；In order to reduce the spy closely located Blind area and effectively control system size are surveyed, there is necessarily overlapping between the transmitting of two-axis laser radar and receiving aperture, will make Blocked into edge.

If detection target is considered as into lambertian, amount of radiation and the direction of the point source into space in prescribed direction in solid angle It is relevant with surface normal direction, therefore need to consider sampled point G in fig. 2_(i,j)(X, Y, Z) echo chief ray is with receiving optical axis Angle γ_(i,j)(Z)：

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) it is：

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η₁For the transmissivity of optical transmitting system, η₂To receive The transmissivity of optical system, θ is transmitting optical axis and the angle of 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) asked With obtain the return laser beam gross energy P at detection range Z_d(Z) it is：

P_d(Z)=∑ P_(i,j)(Z) (11)

In overlength distance detection purposes, detector is often placed in the focal plane of receiving optics, for infinite Remote target is detected and (enters window position in infinity)；And, it is necessary to by adjusting detector in short distance detection purposes Image planes position, is detected for limited remote target and (enters window position at limited distance).Therefore, by changing in formula (4) The image planes position L ' of detector, obtains the return laser beam energy P that detector is received at any image planes position_d(Z), contribute to Realize optimal return laser beam energy response.

Specific embodiment

Illustrate the feasibility of the present invention by three examples.Assuming that one way atmospheric transmissivity τ is 0.98, target reflectivity ε is 0.1, the transmissivity η of optical transmitting system₁For 0.9, the transmissivity η of receiving optics₂For 0.85, transmitting optical axis and target The angle theta of face normal is 0 °.Using 3 examples of the 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 distribution in example 1, and Fig. 7 is change of the return laser beam energy in example 1 with detection range Change tendency chart.

Return laser beam energy in Fig. 7 at 1m is 5.71 × 10^-6Return laser beam energy at W, 150m is 9.79 × 10^{- 8}Return laser beam energy reaches maximum 2.09 × 10 at W, 7m^-5W, 1m to return laser beam energy in 150m detection ranges dynamic About 213 times of scope.

Embodiment 2：

Fig. 8 is flat-top laser beam intensity distribution in example 2, and Fig. 9 is change of the return laser beam energy in example 2 with detection range Change tendency chart.

Return laser beam energy in Fig. 9 at 5m is 1.5 × 10^-5Return laser beam energy at W, 500m is 1.39 × 10^-7W, Return laser beam energy reaches maximum 1.53 × 10 at 10m^-5W, 5m to return laser beam energy in 500m detection ranges dynamic model Enclose about 110 times.

Embodiment 3：

Figure 10 is actual measurement semiconductor laser intensity distribution in example 3, and Figure 11 is return laser beam energy in example 3 with detection The changing trend diagram of distance.

Return laser beam energy in Figure 11 at 1m is 5.29 × 10^-6Return laser beam energy at W, 150m is 9.8 × 10^{- 8}Return laser beam energy reaches maximum 6.5 × 10 at W, 7m^-6W, 1m to return laser beam energy in 150m detection ranges dynamic model Enclose about 66.4 times.

Illustrate that laser radar echo energy balane model proposed by the present invention can be used for any laser strong by 3 examples Degree distribution, the coaxial or two-axis laser radar system of any aperture blocking, obtain detector and are received at any image planes position Return laser beam energy.It is emphasized that above-mentioned 3 calculated examples set up saturating in same reflection characteristic goal thing, air Penetrate under the conditions of rate, optical system transmissivity etc., the variability of above-mentioned parameter, return laser beam energy are considered in actual application Change will be produced.

It should be appreciated that for those of ordinary skills, can according to the above description be improved or converted, And all these modifications and variations should all belong to the protection domain of appended claims of the present invention.

Claims (8)

1. backward energy computational methods in a kind of laser radar system, it is characterised in that comprise the following steps：

Step 1, the laser intensity Two dimensional Distribution G fallen into receiving optics visual field is obtained_(i,j)(X,Y,Z)；

Step 2, sampled point G is calculated_(i,j)Effective solid angle ψ of (X, Y, Z) echo beam_(i,j)(Z)；

Step 3, sampled point G is calculated_(i,j)(X, Y, Z) echo chief ray and the angle γ for receiving optical axis_(i,j)(Z)；

Step 4, sampled point G is calculated_(i,j)(X, Y, Z) reflexes to the return laser beam energy P of detector_(i,j)(Z)；

Step 5, return laser beam gross energy P is calculated_d(Z)；

In the step 1, the laser intensity Two dimensional Distribution G fallen into receiving optics visual field_(i,j)(X, Y, Z) is：

G_(i,j)(X, Y, Z)=P₀G(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 receiving optics entrance pupil central coordinate of circle And radius, R is field of view of receiver radius,Receive angle of half field-of view, P₀For incident laser peak power；Square is recorded by defining n × n Battle array A_(i,j)(X, Y) judges whether G (X, Y, Z) is fallen into 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.

2. laser radar system backward energy computational methods according to claim 1, it is characterised in that in the step 2, Sampled point G_(i,j)Effective solid angle ψ of (X, Y, Z) echo beam_(i,j)(Z) acquisition methods are as follows：

If the image planes position of detector is L ', receiving optics enters 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 the sampled point G of window_(i,j)(X, Y, Z) at receiving optics entrance pupil projected outline equation φ (_i,j)(X_w,Y_w,R_w) For：

φ_(i,j)(X_w,Y_w,R_w)=(X_w-X_d)²+(Y_w-Y_d)²-R_w2=0

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

Wherein (X_w,Y_w,R_w) it is the central coordinate of circle and radius projected into window；

The entrance pupil effective area S of receiving optics_(i,j)(Z) it is：

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

S_(i,j)(Z) to remove after the circular shield portions of center and peripheral, window projection and the overlapping area of entrance pupil are entered, wherein (X_d,Y_d, R′_d) centered on shield portions central coordinate of circle and radius, (X_s,Y_s,R_s) be edge shield portions central coordinate of circle and radius, lead to Cross definition m × m record matrix Bs_(i,j)(X, Y) auxiliary is calculated, if B_(i,j)(X, Y) is in entrance pupil effective 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) it is：

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

3. laser radar system backward energy computational methods according to claim 2, it is characterised in that in the step 3, Sampled point G_(i,j)(X, Y, Z) echo chief ray and the angle γ for receiving optical axis_(i,j)(Z) it is：

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

4. laser radar system backward energy computational methods according to claim 1, it is characterised in that in the step 4, Sampled point G_(i,j)(X, Y, Z) reflexes to the return laser beam energy P of detector_(i,j)(Z) it is：

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

Wherein, τ is one way atmospheric transmissivity, and ε is target reflectivity, η₁For the transmissivity of optical transmitting system, η₂To receive optics The transmissivity of system, θ is transmitting optical axis and the angle of target face normal.

5. laser radar system backward energy computational methods according to claim 1, it is characterised in that in the step 5, Return laser beam gross energy P_d(Z) it is：

P_d(Z)=∑ ∑ P_(i,j)(Z)。

6. laser radar system backward energy computational methods according to claim 2, it is characterised in that described arbitrarily enters Laser intensity Two dimensional Distribution G (X, Y, Z) is penetrated to describe by analytic expression, or by CCD camera survey real LASER Light Source come Obtain.

7. laser radar system backward energy computational methods according to claim 3, it is characterised in that described entrance pupil has Imitate area S_(i,j)(Z) computational methods are applied to unobstructed, or many places block and the irregular receiving optics of occlusion shapes.

8. laser radar system backward energy computational methods according to claim 3, it is characterised in that detected by changing The image planes position L ' of device, obtains the return laser beam energy P that detector is received_d(Z)。