CN110018493A - The laser power selection method of two waveband intersection formula active Range-gated Imager system - Google Patents
The laser power selection method of two waveband intersection formula active Range-gated Imager system Download PDFInfo
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Abstract
The present invention relates to a kind of laser power selection method of two waveband intersection formula active Range-gated Imager system, energy of lasers selection inaccuracy in existing laser active illumination is solved the problems, such as.This method includes one) obtaining the laser minimum laser transmission power based on sensitivity；Two) the laser minimum laser transmission power based on contrast is obtained；Three) using numerical value biggish in step 1 and step 2 as the minimum laser transmission power of laser.
Description
Technical field
The present invention relates to imaging systems, and in particular to a kind of laser of two waveband intersection formula active Range-gated Imager system
Power selection method.
Background technique
Electro-optic theodolite is terminal measuring device irreplaceable in the construction of target range, the figure shot by interpretation optical measuring device
As parameters such as the trajectory of available airbound target and postures, such parameter be weapon test identification and accident analysis it is important according to
According to, and the premise for obtaining such parameter is the target image for obtaining high quality.When theodolite tracks dark weak signal target at a distance, or
Under the environment such as cloud, mist, flue dust, low-light (level), how to effectively improve the operating distance of electro-optic theodolite and improve target range image matter
Amount becomes the critical issue for promoting target range electro-optic theodolite system performance.
Active range-gated imaging technique (using the Range-gated Imager system of pulse detection system) has effect
Distance is remote, imaging clearly, can displaying target details, signal noise ratio (snr) of image is high, contrast is high, do not influenced by light source, can be in sleet mist
The characteristics of working under equal bad weather circumstances.Wherein, range gating laser three-dimensional imaging can intuitively obtain target shape abundant
Or basic structure, inhibit background interference, can be used to identify target and target signature position.If by technique of laser range gated imaging technology
Under highly-sensitive detector integrated combination to identical platform, the limit detection ability of system can be greatly promoted, long distance can be solved
Problem is imaged from, dark weak, Small object tracking, the mutual supplement with each other's advantages of Active Imaging and imaging and passive imaging can be made.Low-light (level) class photoelectric transfer
The optical devices such as sensor (single photon image), thermal imaging system, laser radar, laser range finder are all in combination with rangerate-gate technique
To correlated characteristic target imaging, optical system is specifically designed according to factors such as operating distance, target signature, illumination and reaches satisfied
Effect on Detecting.
Assuming that detected target be certain body, detector be EBCCD (electron-bombardment-type charge-coupled device), it is active away from
It is as shown in Figure 1 from the signal of gated imaging system principle.By adjusting the angle of divergence and tracing area of transmitting laser beam, make laser light
Spot covers entire target or illuminates the key feature position of target.The atmospheric background is overcome to radiate, thoroughly using rangerate-gate technique
Cross the influence that the factors such as rate, scattering and absorption and turbulent flow generate image quality.The composition and original of Range-gated Imager system
Reason: laser emits strong short pulse, and pulsed laser irradiation to body returns to EBCCD by the laser of target reflection.When laser arteries and veins
When punching is in back and forth on the way, storbing gate is closed；When reflected light reaches EBCCD, storbing gate is opened, and enables reflected light by light splitting system
Detector is reached after system, the storbing gate unlatching duration matches with laser pulse.
Range-gated imaging technique is according to the effect of relevant parameter (pulsewidth, repetition, power etc.) and target of pulse laser
Distance matches the receiving time of detector to determine, target can be removed from complicated ambient noise, it is backward to cut down atmosphere
Dispersion effect, image-forming principle are as shown in Figure 2.Range-gated Imager system is broadly divided into following sections: pulse laser, control
System and imaging system.In order to promote imaging operating distance, commonly used laser Q-switching technology realizes high-peak power, narrow spaces
Etc. demands, imaging system have the function of external trigger control.Pulse laser launches laser pulse to imaging object, according to target
Reflected light reach the time order and function of imaging system different times to determine the opening and closing of gated imaging device with scattering light.
In the prior art, Laser Active Imaging System Used has been widely used, but transmission of the laser in atmospheric environment is special
Property there are no the researchs of system, science, especially Laser Atmospheric Transmission system transter model is often only used for emulating
It calculates, does not form the engineering calculating method of laser energy decaying, there is a problem of energy of lasers selection inaccuracy.
Summary of the invention
The present invention provides a kind of laser power selection method of two waveband intersection formula active Range-gated Imager system.This hair
Bright laser power selection method is for two waveband intersection formula Range-gated Imager system design, it is intended to solve laser and actively shine
Bright middle energy of lasers selects inaccurate problem.Probe angle of this method in theodolite receiving end is set out, and spy is comprehensively considered
It surveys device sensitivity, contrast, signal-to-noise ratio and atmosphere is combined to analyze pulse laser to influence retrospectively calculate caused by laser transmission
Required minimum energy requirement.
Technical solution of the invention is as follows:
A kind of laser power selection method of above-mentioned two waveband intersection formula active Range-gated Imager system, including following step
It is rapid:
One) the laser minimum laser transmission power based on sensitivity is obtained
1) laser beam solid angle Ω is obtained；
The π of Ω=4 sin2(θ/4)
Wherein, θ is the transmitting full-shape of laser；
2) energy for reaching detector is obtained；
2.1) the energy P reached at target surface is calculated1；
Wherein, P0For the emission peak power of laser；
α1For the angle in radiating laser beams direction and target surface normals；
R1The real-time range of system is received for target range frist theodolite unit；
ηatFor one way atmospheric transmittance；
AbThe area being irradiated with a laser for target；
2.2) the radiation energy P of target is obtainedt；
Pt=P1·ρ0
Wherein, ρ0For target surface reflectivity；
2.3) the energy P for reaching detector is obtainedr；
Wherein, R2The real-time range of system is received for target range second theodolite unit；
α2For the angle of target surface normals and detector target surface；
ηatfFor return atmospheric transmittance；
AsFor detector entrance pupil area；
τrFor the preposition transmissivity of optical system of detector；
3) the laser minimum laser transmission power P based on sensitivity0；
Two) the laser minimum laser transmission power based on contrast is obtained；
Pv=P0F=6.76210-410000=6.762W
Three) using numerical value biggish in step 1 and step 2 as the minimum laser transmission power of laser.
Compared with prior art, the present invention beneficial effect is:
1. laser power selection method of the invention considers that target image obtains quality in all directions, hair is brought out from detector,
It is reversely counted using the quality index of sensitivity, contrast, signal-to-noise ratio as examination image in conjunction with the influence that atmosphere transmits laser
Energy of lasers is calculated, this method is simple and reliable, can be used as the selection gist of laser power in the case of long distance laser active illumination.
Under the premise of laser energy selection is accurate, data reference is also provided in the energy spectrometer that laser reaches target side.
2. the present invention is provided according to laser transmission link model in the minimum energy of detector end inverse pulse laser
The data supporting of pulse laser selection.
Detailed description of the invention
Fig. 1 is existing active Range-gated Imager system principle schematic diagram；
Fig. 2 is existing range-gated imaging technique schematic illustration；
Fig. 3 is that two waveband of the present invention intersects formula active illumination Range-gated Imager System Working Principle figure；
Fig. 4 is frist theodolite composition block diagram in the present invention；
Fig. 5 is double-view field transceiver optical module schematic diagram in the present invention.
Appended drawing reference: 1- first laser device, 2- second laser, the ground 3- interactive managing system, the first detector of 4-, 5-
Frist theodolite, the second detector of 6-, 7- second theodolite, 8- double-view field transceiver optical module, 81- transceiver insulation dress
It sets, 82- long short focus image-forming objective lens group, 83- principal reflection mirror, 84- secondary mirror.
Specific embodiment
The contents of the present invention are described in further detail below in conjunction with the drawings and specific embodiments:
In order to improve target range optoelectronic device to the detectivity of remote dark weak signal target, accelerate active Range-gated Imager
Technology target range engineer application process, the present invention provide a kind of two waveband intersection formula active illumination Range-gated Imager system and
Imaging method.Two waveband intersects formula active illumination Range-gated Imager system and uses two theodolite cloth station schemes, the first longitude and latitude
The pulse laser that 532nm and 1064nm is respectively adopted in instrument unit, second theodolite unit illuminates long-distance flight target.
Receiving end uses range gating system, and detector is the EBCCD of different quantum efficiencies (according to laser wavelength type selecting).The present invention exists
On the basis of considering laser link transmission, propose in detector end group in sensitivity, contrast, three aspect index inverse of signal-to-noise ratio
Pulse laser index；Pulse laser direction calculation has been derived in the case where measurement pattern is not landed in target range, has finally devised double-view field
The optical module of transceiver.
Two waveband intersects formula active illumination Range-gated Imager system as shown in figure 3, including frist theodolite unit, second
Theodolite unit, first laser device 1, second laser 2 and ground interactive managing system 3；Frist theodolite unit includes first
Detector 4 and frist theodolite 5；Frist theodolite 5 carries first laser device 1 and the first detector 4, second theodolite unit packet
The second detector 6 and second theodolite 7 are included, second theodolite 7 carries second laser 2 and the second detector 6；First laser device
1 is different with the wavelength of second laser 2, interact formula illumination to target, the first detector 4 receives second laser 2 and irradiates
It diffuses to what target was formed, the second detector 6 receives first laser device 1 and is irradiated to diffusing for target formation；First
Theodolite unit and second theodolite unit realize the opening of storbing gate by the progress signal communication of ground interactive managing system 3
With closing.
In the present embodiment, the first pulse laser that frist theodolite unit carries issues the laser pulse of 532nm,
Middle a part of directive pre-imaging target, while first pulse laser passes through ground interactive managing system 3 to second theodolite list
Member issues a Q signal (realizing the demands such as high-peak power, narrow spaces by laser Q-switching technology).Second theodolite list at this time
The storbing gate of member is closed, and no signal enters the detector of second theodolite unit, after certain delay time T, the
One theodolite unit gives one trigger signal of storbing gate of second theodolite unit, the second warp by ground interactive managing system 3
The storbing gate of latitude instrument unit opens a period of time, and the 532nm laser irradiation for allowing frist theodolite unit to emit is formed to target
Diffuse into the detector of second theodolite unit, make second theodolite unit obtain target two-dimensional intensity picture.When sharp
When light pulse is transmitted in the sky, the storbing gate of second theodolite unit is closed, and scattering light cannot be introduced into detector formation and make an uproar
Sound, to improve signal-to-noise ratio, delay time T is according to the real-time range of frist theodolite unit, second theodolite unit and target
It calculates.
Similarly, the second pulse laser that second theodolite unit carries issues the laser pulse of 1064nm, wherein one
Divide directive pre-imaging target, while second theodolite unit is issued by ground interactive managing system 3 to frist theodolite unit
One Q signal, the storbing gate of frist theodolite unit is closed at this time, and no signal enters the detector of frist theodolite unit,
After certain delay time T, second theodolite unit is by ground interactive managing system 3 to frist theodolite unit
The storbing gate of one trigger signal of storbing gate, frist theodolite unit opens a period of time, and second theodolite unit is allowed to emit
1064nm laser irradiation diffuse to what target was formed into the detector of frist theodolite unit, make frist theodolite list
Member obtains target two-dimensional intensity picture.
The present invention has comprehensively considered application environment and target property, root using the pulse laser of 532nm and 1064nm wave band
According to the difference of service condition, laser wavelength can be selected according to other demands, such as: 450nm, 808nm, 1.54 μm, 10.6 μm etc..
The detector that the present invention uses for EBCCD, also it is replaceable for the low-light (level)s class photoelectric sensor such as ICCD, BCCD, thermal imaging system,
The optical devices such as laser radar, laser range finder, polarization camera.
Two waveband intersection formula active illumination Range-gated Imager system discussion of the present invention is two transits cloth station, similarly,
This method can also apply the Convergent measurement with optoelectronic devices such as gondolas.The two waveband pulse laser lighting that the present invention studies can also expand
Exhibition is that multi-band pulse laser illuminates, and can obtain more target optical spectrum response characteristics.Active distance choosing proposed by the present invention
Logical imaging method can also be changed to continuous irradiation mode, that is, be replaced into continuous wave laser.
Frist theodolite 5 of the invention, second theodolite 7 are all made of existing apparatus, and are the identical device of structure.First
Theodolite 5 carries 532nm pulse laser, and second theodolite 7 carries 1064nm pulse laser.Frist theodolite 5, second passes through
Latitude instrument 7 is mainly divided by track frame, SERVO CONTROL subsystem, operation control subsystem, image interpretation subsystem, image recording
Composition, the basic composition block diagrams of system such as system, integrated carrier vehicle, time terminal, communication interface, ancillary equipment are as shown in Figure 4.Each point
System composition and function are as follows: track frame includes precision bearing system, torque motor, encoder, measuring mechanism etc. of not taking a seat, for holding
Each detector is carried, angle measurement is completed, executes tracking.The servo antrol of SERVO CONTROL subsystem completion track frame.Operation control, which divides, is
System include operating console, management computer, data interaction computer, each detector image monitor, the hardware such as ups power and
Corresponding control software, the main operation control for completing equipment, image is shown and external information exchange.Image interpretation subsystem is used for
Interpretation, image analysis and the calculating for completing image, provide measurement data.Image recording subsystem includes digital image recording portion
Point, hard disk video recorder and CD writer etc., digital image recording part real non-destructive records the digital picture of each detector, firmly
Disk video recorder records the analog video image of multiple detectors；Image data, measurement data are burnt at CD by CD writer
On, convenient for saving.When GPS+ Beidou/B code time terminal is for receiving GPS/ Beidou time, IRIG-B code data, providing unified
Between benchmark and provide synchronization signal for other subsystems, integrated carrier vehicle provides transport for equipment and uses platform.
As shown in figure 5, the present invention is according to use environment, in the optical path of first laser device 1 and the first detector 4, second swash
Double-view field transceiver optical module 8, double-view field transceiver optics are provided in the optical path of light device 2 and the second detector 6
Component 8 includes preposition beam-expanding system, transceiver insulation device 81 and long short focus image-forming objective lens group 82.
Preposition beam-expanding system mainly realizes the collimation to laser beam, to realize long distance illumination.It uses two to be total to
Burnt parabolic mirror composition, structure is simple, by using off axis, avoids influence of the central obscuration to energy.In addition, this is tied
Construction system coma is zero, therefore has biggish visual field, reduces the aberration correction pressure of rear image-forming objective lens group.
Transceiver insulation device 81 is real by Brewster beam splitting chip for transmitting laser signal to be isolated and receives laser signal
The now reflection to transmitting laser signal and the transmission for receiving laser signal.
Long short focus image-forming objective lens group 82 passes through the method cut out and realizes the switching of the long short focus of system, to realize big view
Field search is switched fast with small field of view high-resolution imaging.
Laser emission optical path sequence: laser light source emits laser, reflexes to secondary mirror 84 by transceiver insulation device 81,
Optical path convergence is reflexed to principal reflection mirror 83 by secondary mirror 84, is issued illuminating bundle by principal reflection mirror 83.
Detector receives target light sequence: target scattering light is reflected and saturating after principal reflection mirror 83 by secondary mirror 84
Transceiver insulation device 81 is penetrated, the detector of EBCCD is entered after long short focus image-forming objective lens group 82 (i.e. zoom switch groups).
Optical system parameter is as shown in the table:
2 optical system parameter of table
| Optical system parameter | Numerical value | Optical system parameter | Numerical value |
| Laser beam divergence | 1mrad | Receive system focal length | 400/800mm Switch-zoom |
| Spot diameter | 4mm | F number | 5 |
| Expand ratio | 5× | Parameter detector | 1280 × 1024,6.7 μm |
At spatial frequency 74lp/mm >=0.4, image quality is good, can satisfy system by long short focus imaging system MTF
Requirement to target blur-free imaging.For beam-expanding system in such a way that two off axis paraboloidal mirrors are focused, design result reaches diffraction
The limit, wave aberration can be very good the requirement for meeting beam-expanding system close to zero.
In present system, according to the laser link mode of building, in the base for considering the factors such as laser atmospheric attenuation
On plinth, the minimum of pulse laser is calculated in many-sided emphasis such as sensitivity, picture contrast, signal-to-noise ratio in detector end group
Index request gives the selection gist of pulse laser power.
Under the conditions of atmospheric visibility is not more than 70% not less than 10km, relative humidity, it is assumed that target is certain guided missile, to allusion quotation
Type body (5.0m × 1.0m) target acquisition distance is not more than 60km.Assuming that frist theodolite unit, second theodolite unit with
The distance of target is 60km.
For be still when guaranteeing this system limit operating distance Area Objects detection, it can be assumed that typical body target is detecting
5 × 1 pixels are occupied when distance 60km on target surface, then corresponding focal length focal length can be calculated by formula:
Y'=(L/R) × f'(1)
In formula: y'-target picture size；L-target size；R-operating distance；
According to the detector of selection and systematic technical indicator requirement, detector resolution 1280 × 1024, pixel dimension 6.7
It μm * 6.7 μm (EBCCD), calculates and obtains focal length f'=402mm, take f'=400mm.
The disperse spot diameter that diffraction is formed should match with detector Pixel size, disperse spot diameter d:
D=2.44 λ F (formula 1)
In formula: d~disperse spot diameter；λ~optical wavelength；F~optical system F number.
When circumscribed circle diameter is 0.00947mm, λ=0.00055mm:
In order to guarantee projectile energy, the detectivity of system is improved, selection system relative aperture is F/5.5.
Equivalent clear aperture D is calculated according to the following formula
It obtains D=72.7mm, takes D=80mm.
Detector target surface can be calculated having a size of 8.576mm × 6.86mm；Focal range is 25mm~400mm, under
Face formula can calculate system visual field:
In formula,For angle of half field-of view, h is image height, and f' is system focal length.When system focal length corresponding visual field be 1.228 ° ×
0.9825°；Corresponding visual field is 18.93 ° × 15.34 ° when system short focus.
In laser transmission link, the energy of laser source and efficiency, transmitter shake, detector reception mode and effect
The combined factors such as rate, Laser Atmospheric Transmission efficiency, atmospheric agitation, the beam diffraction limit affect the index Design and target of system
Picture quality.
Appearance with size for 5.0m × 1.0m is designated as computing object, and the reflected energy of target reaches detector end optical power
It is known.The COMPREHENSIVE CALCULATING pulse laser energy in terms of three.First, the signal light energy that detector receives should be greater than
Detector Equivalent noise energy (detector sensitivity), the starting point that entire downlink transfer Link energy calculates at this time become detecting
Device is in the minimum response problem of incident optical energy.Second, for Area Objects, target energy and background energy that detector receives
Contrast requirement must be able to satisfy.Third, the signal light quantum number that detector is converted should be greater than the stray lights such as sky background institute
The light quantity subnumber (signal-to-noise ratio) of conversion.
A) meet detector sensitivity demand
It is R by laser transmitting system transmitting Laser beam propagation to the distance of frist theodolite unit1Target at, if swash
The emission peak power of light device is P0, transmitting full-shape is θ, and laser beam solid angle is the π of Ω=4 sin2(θ/4) reach target surface
Illumination are as follows:
In formula, α1For the angle in radiating laser beams direction and target surface normals, ηatFor one way atmospheric transmittance.
Reaching the energy at target surface is
In formula, AbFor the area that target is irradiated with a laser, if ρ0For target surface reflectivity, then the radiation energy of target
Are as follows:
Pt=P1·ρ0(formula 7)
Know its luminous intensityThen reach the illumination at reception system entrance pupil are as follows:
In formula, R2The real-time range of system, α are received for target range second theodolite unit2For target surface normals and visit
Survey the angle of device (EBCCD) target surface, ηatfFor return atmospheric transmittance, it is assumed herein that being equal with one way atmospheric transmittance.It reaches
Energy on detector are as follows:
In formula: AsFor detector entrance pupil area, τrFor the preposition transmissivity of optical system of detector.
If PrMeet photodetector (EBCCD) minimum detectable power.It can be obtained by formula (6)~formula (10), be visited meeting
When surveying device sensitivity index, required minimum laser transmission power are as follows:
Parameters, that is, variable basis for selecting and numerical value such as table 1:
1 parameter selection of table and foundation
When laser beam passes through propagation in atmosphere, atmospheric attenuation effect and turbulence effect can be generated.Atmospheric turbulence effect is not
Directly cause the decaying of laser energy, and cause energy attenuation principal element be laser beam intensity, phase fluctuation and light
Phenomena such as beam drift shake, therefore the attenuation effect of atmosphere is that laser energy calculates the principal element to be considered.
Due to vertical transfer laser attenuation calculate it is sufficiently complex, engineer application field usually by vertical decrease it is equivalent at
The decaying of certain level distance is calculated.Horizontal air transmitance can indicate are as follows:
Wherein, kλiAbsorption coefficient for i-th kind of gas molecule to the wavelength, αλIt is atmospheric molecule to the scattering system of the wavelength
Number, βλIt is aerosol to the scattering coefficient of the wavelength.The atmospheric attenuation of the optical maser wavelength of 532nm is mainly dissipating for atmospheric aerosol
It penetrates, other attenuations can be ignored.Its attenuation coefficient can be described with visibility, generally be calculated with following formula in engineering:
In formula, V is visibility, and unit km, λ are optical maser wavelength, and unit μm, ξ is experience number, when visibility is greater than 6km
ξ=1.3 are taken, average visibility is 10~12km, takes 10km.It is molten to substitute into gas when the available 532nm laser level of above formula transmits
The attenuation coefficient of glue:
It is complex that laser passes through the case where when atmosphere inclination (or vertical) is transmitted, it is assumed that and it is θ that laser, which tilts transmission of angle,
The transmitance of atmosphere is calculate by the following formula:
Wherein function f is proper general graceful function, slantwise attenuation is equivalent to horizontal distance decaying, above formula can become:
RkiFor the equivalent level transmission range of i-th of absorption factor, RαFor the equivalent level transmission range of molecular scattering, Rβ
For the equivalent level transmission range of aerosol scattering.It is penetrated in conjunction with the SEQUENCING VERTICAL that colloidal sol attenuation coefficient obtains the wavelength laser
Rate:
Tθ=exp (- βλRβ) ≈ 0.4245 (formula 16)
The above transmitance is calculated by formula and experience, and Lowtran can also be used in transmitance or Motran is soft
Part, which calculates, to be obtained, the atmospheric transmittance (input condition: middle latitude summer area, rural delustring system calculated by Lowtran software
Number Vis=23km, no sexual intercourse, wave-length coverage 4nm).The transmitance that two methods are calculated is approximately equal, takes 532nm wave band
Laser one way atmospheric transmittance be 0.4.
The minimum detectable power (sensitivity of EBCCD) of detector
Selected EBCCD sensitivity is in 3e-/count or so.
ηqeFor the conversion quantum efficiency of EBCCD (wavelength 532nm is 50%).So due to laser pulse on 14.14km back and forth
Transition time is 93.3 μ s, so gate pulse should postpone 93.3 μ s behind bright pulse forward position.(pulse laser is ginseng with energy
Number index, laser repetition rate 10kHz).If the gate width of EBCCD is 1 μ s, then the time for exposure, also approximation was selected as 1 μ s.
Meet the P that the minimum detection of EBCCD requiresrFor Pr=E/Ts=7.46610-19/(1·10-6)=7.46610-13W (formula 18)
Wherein, SPFor EBCCD picture dot size.So, the emission peak power of pulse laser
P0=5.326104W (formula 19)
So, the pulsewidth of pulse laser is set as 2ns, and an emitted energy is E=P0·Wp=5.326104·2·
10-9=1.0610-4J (formula 20)
The mean power of pulse laser
Pv=P0F=1.0610-410000=1.06W (formula 21)
In conclusion the minimum power of pulse laser is 1.06W when meeting detector sensitivity index request.
B) meet detector contrast demand
The illumination that target and background reach detector, which meets following formula relationship, can meet the contrast minimum requirements of imaging.
Nighttime image Analysis of Contrast
Target illuminance is made of moonlight reflection, atmospheric scattering light, ground return light and several parts of laser reflection.
In formula, EeFor the effective target illuminance (signal) for reaching detector surface；ESFor moonlight reflection, atmospheric scattering light,
The illumination of ground return light etc. (being referred to as natural light) arrival detector surface；EtDetector is reached for the target light of laser reflection
The illumination on surface.
The luminous energy of earth's surface illumination comes from moonlight, the vault of heaven brightness and atmospheric scattering light.Target surface mainly reflects moonlight, big
Gas scatters light and ground return light.Target surface is B by the total brightness of natural light irradiationMesh, the surface that target is irradiated by moonlight is bright
Degree is B1, target is B by the brightness that atmospheric scattering light and earth surface reflection light irradiate2, then:
In formula: ρ0~target surface diffusing reflection coefficient；E1~the moon illuminance；E2~earth surface reflection light and atmospheric scattering illumination
Degree, that is, correspond to the illumination under shade.When full moon and illuminance of ground is 0.1lux, E when the moon angle of elevation is 45 °2=0.01lux, then:
Illumination E of the natural light of target reflection on target surfaceS
The B that will be calculatedMesh=1.9610-6Stilb and the equivalent clear aperture of optical system, D=80mm, f '=
400mm, τr=0.5, ηat=0.4 substitutes into above formula:
Having the sunny night sky of the moon to take sky background brightness is 110-6Stilb.Illumination of the sky background on target surface
Pass through contrast minimum requirements inverse energy of lasers.Night under the premise of having laser lighting, target and sky shape
At the bright target of dark background condition.
Due to ES=1.230810-4Lux, then, it is known that Et≥4.177·10-5lux(EtFor the target light of laser reflection
The illumination for reaching detector surface, according to view apperception function Vλ(1W=683lm, λ=555nm), takes Vλ=260) E can, be obtainedt≥
1.606·10-7W/m2.Inverse obtains the peak power of pulse laser transmitting
P0=3.381105W (formula 31)
So, the pulsewidth of pulse laser is set as 2ns, and an emitted energy is E=P0·Wp=3.381105·2·
10-9=6.76210-4J (formula 32)
Laser minimum laser transmission power based on contrast
Pv=P0F=6.76210-410000=6.762W (formula 33)
Day images Analysis of Contrast
Calculating analysis is carried out using same procedure, on daytime without laser lighting mode, target forms bright with sky
The dark target of background condition, and meet contrast demand.
In the present invention, has studied target range and do not land the real-time direction calculation of pulse laser beam in measuring.It is not fallen in target range
It is usually more demanding to ground flat degree when ground measures, and the rigidity of car body supporting mechanism and gap result in theodolite survey
With the axis error that hangs down when amount, and the error constantly changes with external disturbance.For environmental suitability and the survey for improving theodolite
Mobility is measured, using the posture information for the POS real-time measurement theodolite being installed on theodolite pedestal.First is not entered in target
Theodolite unit, second theodolite unit visual field when, target is introduced into visual field generally according to guidance information, according to theodolite
Longitude and latitude, elevation information, posture information are tested the real-time track of aircraft, are converted by corresponding coordinate, calculate theodolite
Azimuth, pitch angle are given.Detailed process is as follows:
Assuming that the track of tested aircraft includes longitude, latitude, height respectively (λp,Lp,hp) geographical location point, will
The real-time longitude of theodolite, the latitude, height (λ of POS outputT, LT, hT) be all transformed under space coordinates with tested point position
(WGS84 or place coordinate system).After conversion, the spatial coordinate location of theodolite is (xp,yp,zp), tested point spatial coordinate location
For (xT,yT,zT), theodolite unit sight vector D is sought according to the two coordinate.
WithFor the absolute distance of object to be measured and theodolite.
According to the real-time position information (longitude, latitude, height) of theodolite, unit pointing vector D is indicated to navigation to sit
(northeast day coordinate system) obtains D under mark systemN.It will be under navigational coordinate system according to the azimuth of theodolite carrier vehicle, pitch angle, roll angle
Pointing vector DNIt is transformed under theodolite carrier vehicle coordinate system,
Wherein, θ, P, R are respectively the azimuth of theodolite carrier vehicle, pitch angle, roll angle.
Since theodolite has two orientation, pitching movement dimensions, sight vector is indicated in theodolite coordinate system, works as warp
Azimuth A, the pitch angle E of latitude instrument when being 0 initial sight vector be N0, carried then can be calculated and be obtained by following formula in theodolite
Sight vector in vehicle coordinate system.
Enable DP=N counter can solve azimuth A, the pitch angle E of theodolite, be realized according to the theodolite angle being calculated
The real-time high-precision of moving target is directed toward and illumination.
Claims (1)
1. a kind of laser power selection method of two waveband intersection formula active Range-gated Imager system, which is characterized in that including
Following steps:
One) the laser minimum laser transmission power based on sensitivity is obtained；
1) laser beam solid angle Ω is obtained；
The π of Ω=4 sin2(θ/4)
Wherein, θ is the transmitting full-shape of laser；
2) energy for reaching detector is obtained；
2.1) the energy P reached at target surface is calculated1；
Wherein, P0For the emission peak power of laser；
α1For the angle in radiating laser beams direction and target surface normals；
R1The real-time range of system is received for target range frist theodolite unit；
ηatFor one way atmospheric transmittance；
AbThe area being irradiated with a laser for target；
2.2) the radiation energy P of target is obtainedt；
Pt=P1·ρ0
Wherein, ρ0For target surface reflectivity；
2.3) the energy P for reaching detector is obtainedr；
Wherein, R2The real-time range of system is received for target range second theodolite unit；
α2For the angle of target surface normals and detector target surface；
ηatfFor return atmospheric transmittance；
AsFor detector entrance pupil area；
τrFor the preposition transmissivity of optical system of detector；
3) the laser minimum laser transmission power P based on sensitivity0；
Two) the laser minimum laser transmission power based on contrast is obtained；
Pv=P0F=6.76210-410000=6.762W
Three) using numerical value biggish in step 1 and step 2 as the minimum laser transmission power of laser.
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