CN110471046A - A kind of Differential Absorption Laser Radar System constant calibrating method - Google Patents
A kind of Differential Absorption Laser Radar System constant calibrating method Download PDFInfo
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- CN110471046A CN110471046A CN201910807136.6A CN201910807136A CN110471046A CN 110471046 A CN110471046 A CN 110471046A CN 201910807136 A CN201910807136 A CN 201910807136A CN 110471046 A CN110471046 A CN 110471046A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/497—Means for monitoring or calibrating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
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- Computer Networks & Wireless Communication (AREA)
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- Radar, Positioning & Navigation (AREA)
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- Investigating Or Analysing Materials By Optical Means (AREA)
- Optical Radar Systems And Details Thereof (AREA)
Abstract
The present invention relates to a kind of Differential Absorption Laser Radar System constant calibrating methods, belong to laser radar detection technical field.This method comprises the following steps: (1) placing the first photodetector, absorption cell and hard target respectively at system exit laser；Absorption cell position is adjusted, the first photodetector is placed on absorption cell front end, as monitoring signal and initial on, the monitoring of off energy；(2) absorption cell is vacuumized using vacuum pump, then pours the object gas that normal concentration is 20000ppm, records the pressure in absorption cell；(3) laser is opened, records the first photodetector, on the and off signal that the second photodetector detects using data acquisition card；(3) radar system constant is determined according to collected data,Absorption cell and hard target are removed, normal Atmospheric Survey is carried out, using improved inversion formula, carries out normal gas concentration detection.This method is monitored implementation record laser state to the primary power of laser, improves data reliability.
Description
Technical field
The present invention relates to a kind of Differential Absorption Laser Radar System constant calibrating methods, belong to Airborne Lidar survey technology neck
Domain.
Background technique
The important tool that laser radar is monitored as environmental contaminants has strong antijamming capability, spatial resolution height, visits
Survey high sensitivity, the measurement advantages such as optical length, be widely used in aerosol, ozone, in atmosphere all kinds of polluted gas detection.
The one kind of differential absorption lidar as laser radar is the new technology in environment in recent years monitoring field, is widely used in
The concentration of polluted gas detects.It passes through the laser of two beam equal-wattage different wave lengths of transmitting, wherein a branch of wavelength is located at target
Near gas absorption spectrum line absorption peak, referred to as on wavelength, another Shu Bochang are located at object gas absorption line the lowest point, referred to as
Off wavelength.Object gas is different to the absorption intensity of two beam laser, so that the decaying of atmospheric scattering echo-signal is different, passes through inspection
The intensity difference for surveying this two beams reflected light can calculate the concentration of tested gas in an atmosphere.Differential absorption lidar system
The light source of system generally uses two beam laser of a laser radar alternate emission or two lasers while emitting two beam laser
Method, and space exploration also needs to use the equipment such as three-dimensional turntable, it is complex for other systems.Due to complexity
Two beam laser of characteristics of optical path and differential absorption lidar wavelength it is different, often in actual detection on wavelength and
The primary power of off wavelength laser is not identical, and the conjunction beam of on and off two-way laser laser in actual detection is not necessarily
The stage being completely coincident can be reached, especially ultraviolet, when the invisible wave band such as infrared is detected, since laser is invisible,
Beam quality closes Shu Xiaoguo and all hardly results in guarantee, this can be such that differential absorption lidar inverting target gas levels cause centainly
Error, its inverting error will be directly resulted in by differing biggish laser radar for those on wavelength and off wavelength energy.
Summary of the invention
The invention proposes a kind of Differential Absorption Laser Radar System constant calibrating method, this method can effectively solve difference
Absorption lidar on wavelength and off wavelength laser energy differ, power jitter, mutation and introduce systematic error, and to swash
The primary power of light is monitored implementation record laser state, improves data reliability.
The present invention is to solve its technical problem to adopt the following technical scheme that
A kind of Differential Absorption Laser Radar System constant calibrating method, includes the following steps:
(1) the first photodetector, absorption cell and hard target are placed respectively at system exit laser；Adjust absorption cell position
It sets, the first photodetector is placed on absorption cell front end, as monitoring signal and initial on, the monitoring of off energy；
(2) absorption cell is vacuumized using vacuum pump, then pours the object gas that normal concentration is 20000ppm, records suction
Pressure in receives pond；
(3) laser is opened, records the first photodetector using data acquisition card, the second photodetector detects
On and off signal；
(4) radar system constant is determined according to collected data, remove absorption cell and hard target, carry out normal atmosphere spy
It surveys, using improved inversion formula, carries out normal gas concentration detection.
The laser uses mid-infrared laser device.
First photodetector be in infrared VIGO PVI-4TE model photodetector.
Second photodetector be in infrared VIGO PVI-4TE model photodetector.
The hard target uses the aluminum hardboard of high reflectance.
Beneficial effects of the present invention are as follows:
1, detection is by the variation of the optical signal before and after absorption cell, to calculate the gas concentration in absorption cell, and with absorption
Pool gas concentration compares, and determines that laser radar whole system corrects constant, the constant is introduced in actual detection, at the beginning of laser
The caused error of the problems such as beginning energy does normalized, and laser primary power is effectively reduced and differs, shake.
2, it monitors laser primary power situation in real time, records every beam on and off energy, achieve the effect that real-time detection.
3, this method particularly suitable for ultraviolet, correct by the system of the invisible wave band differential absorption lidar such as infrared,
Inversion error caused by being greatly reduced using this method due to itself deficiency of system.
4, this method on the basis of original Differential Absorption Laser Radar System by additionally disposing an initial laser detection
Device, an interim absorption cell, interim target to determine the system constants of entire laser radar, then pass through improved inversion formula
The concentration of object gas in inverting atmosphere.
5, the present invention monitors initial laser energy by the first photodetector, and initial laser energy is introduced into difference
It in point absorption lidar equation, substantially reduces since laser primary power differs, the problems such as laser energy is shaken is caused
Inversion error, the retrieving concentration result made are more accurate.
Detailed description of the invention
Fig. 1 is improved system construction drawing, wherein 1 is laser, and 2 be light combination mirror, and 3 be the first photodetector, 4
It is absorption cell, 5 be the one 45 ° of total reflective mirror, and 6 be the 2nd 45 ° of total reflective mirror, and 7 be the 3rd 45 ° of total reflective mirror, and 8 be the 4th 45 ° of total reflective mirror,
9 be the 5th 45 ° of total reflective mirror, and 10 be hard target, and 11 be the trans- telescope of ox, and 12 be the second photodetector, and 13 be data acquisition card,
14 be industrial personal computer.
Fig. 2 is calibration inversion process figure.
Specific embodiment
The present invention is described in further details below in conjunction with attached drawing.
For the present invention by taking a set of general Differential Absorption Laser Radar System as an example, which mainly includes laser thunder
Up to emission system, laser radar receives system and master control system；Wherein, laser radar emission system includes laser 1, closes beam
Mirror 2, the 1st ° of total reflective mirrors, 5, the 2nd 45 ° of total reflective mirrors 6, the 3rd 45 ° of total reflective mirror 7, the 4th 45 ° of total reflective mirror 8, the 5th 45 ° of total reflective mirror
9, wherein the 3rd 45 ° of total reflective mirror 7, the 4th 45 ° of total reflective mirror 8, the 5th 45 ° of total reflective mirror 9 constitute a three-dimensional turntable and hard target 10；Swash
It includes the trans- telescope 11 of ox, the first photodetector 3, the second photodetector 12 and data acquisition card that optical radar, which receives system,
13；Master control system is connect with laser 1, three-dimensional turntable, data acquisition card 13 respectively using industrial personal computer 14, saves data acquisition card
13 collect the first photodetector 3, the experimental data of the second photodetector 12.It is as shown in Figure 1 improved system knot
Structure, the first photodetector 3, the second photodetector 12 record laser primary power signal and laser echo signal respectively.
Whole system constant calibration process is to close beam position end one inside of placement in laser first and pour known concentration
The absorption cell 4 of object gas places a hard target 10 outside system blind area, it is initial to record laser by the first photodetector 3
Signal, the second photodetector 12 record echo-signal, reuse differential absorption lidar formula inverting gas concentration with
Actual absorption pool gas concentrations versus determines system constants C, finally withdraws absorption cell 4 and hard target 10, is visited using the first photoelectricity
Device 3 and the second photodetector 12 are surveyed, system constants C carries out normal gas concentration detection.
Inversion method improves:
According to differential absorption lidar equation, pulse echo power Pon,offIt can indicate are as follows:
A is the area of telescope, P in equationtFor peak power, c is the light velocity, and η is to receive system effectiveness, and β (R) is atmosphere
Backscattering coefficient, α (R) are atmospheric extinction coefficient, and N (R) is Gas concentration distribution, σon,ofFor the differential absorption cross-section of gas, R
It is object at a distance from detector, τ is laser radar system transmitance.
Logarithm, then passage path is asked to find out the concentration information of object gas on and off echo signal intensity ratio first,
The concentration of object gas is finally transformed into according to avogadros constant and gas molecular mass by international standard concentration unit.By
It is closer in the wavelength of two beam laser, so ignoring other correction terms, target gas levels can be with table on last entire path
It is shown as:
Wherein Δ R is the entire path length that light beam passes through, and Δ σ is the differential absorption cross-section of on and off, Poff1For off
Laser primary power, Pon1For on laser primary power, Poff2For off laser irradiation to hard goal back echo signal, Pon2For on
For laser irradiation to hard goal back echo signal, previous differential absorption lidar only records Pon2, Poff2Signal, generally recognize
For Poff1, Pon1Energy it is equal and be added without consideration, generally believeRatio be constant be 1, but this way meeting
Large error is introduced to target gas levels inverting, especially when the initial laser energy of on and off not etc. or energy shakiness is trembled
Move excessive, this method will effectively solve the problems, such as this.
The inversion equation used may be expressed as:
Wherein C is entire radar system constant, that is, we calculate the result of inverting using hard target absorption experiment.We
It will be according to descending method to determine system constants C.
The step of being illustrated in figure 2 entire scaling scheme.
Step 1: placing the first photodetector 3, absorption cell 4, hard target 10 respectively in whole system suitable position；Adjustment
4 position of absorption cell, passes through system light path completely inside absorption cell 4, gets to hard target, guarantees 4 front and back optical path of taking and placing absorption cell
Position first detector 3 that do not change is placed on 4 front end of absorption cell, as monitoring signal and initial on, the monitoring of off energy.
Step 2: absorption cell 4 is vacuumized using vacuum pump, then pour the object gas that normal concentration is 20000ppm, note
Record the pressure in lower absorption cell 4.
Step 3: opening laser 1, the first photodetector 3, the second photodetection are recorded using data acquisition card 13
On the and off signal that device 12 detects.
Step 4: constant C is determined according to collected data, first according to the equation of gas state
PV=NRT (4)
Wherein P is pressure in absorption cell, and V is absorption cell volume, and R is gas constant, and T is environment temperature, and N is in absorption cell
The concentration of object gas, and the physical quantity for needing to acquire.
Step 5: being brought into formula (3) again according to the N that formula (4) is calculated, Δ σ Δ R is it is known that Pon1, Poff1For
First detector, 3 detection data, Pon2, Poff2For the echo-signal that the second detector 12 detects, formula (3) is unique at this time
Unknown quantity only has Constant System constant C, and system constants C can be calculated by formula (3).
Step 6: removing absorption cell 4 and hard target 10, normal Atmospheric Survey is carried out, uses improved inversion formula
(3), normal retrieving concentration can be carried out.
Claims (5)
1. a kind of Differential Absorption Laser Radar System constant calibrating method, which comprises the steps of:
It is placed respectively at system exit laser the first photodetector (3), absorption cell (4) and hard target (10)；Adjust absorption cell
(4) position, the first photodetector (3) are placed on absorption cell (4) front end, as monitoring signal and initial on, off energy prison
Control；
Absorption cell (4) is vacuumized using vacuum pump, then pours the object gas that normal concentration is 20000ppm, records absorption cell
(4) pressure in；
It opens laser (1), is recorded the first photodetector (3) using data acquisition card (3), the second photodetector (12)
On the and off signal detected；
Radar system constant is determined according to collected data,Absorption cell (4) and hard target (10) are removed, normal atmosphere spy is carried out
It surveys, using improved inversion formula, carries out normal gas concentration detection.
2. a kind of Differential Absorption Laser Radar System constant calibrating method according to claim 1, which is characterized in that described
Laser (1) uses mid-infrared laser device.
3. a kind of Differential Absorption Laser Radar System constant calibrating method according to claim 1, which is characterized in that described
First photodetector (3) be in infrared VIGO PVI-4TE model photodetector.
4. a kind of Differential Absorption Laser Radar System constant calibrating method according to claim 1, which is characterized in that described
Second photodetector (12) be in infrared VIGO PVI-4TE model photodetector.
5. a kind of Differential Absorption Laser Radar System constant calibrating method according to claim 1, which is characterized in that described
Hard target (10) uses the aluminum hardboard of high reflectance.
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Cited By (3)
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| CN114637030A (en) * | 2022-05-18 | 2022-06-17 | 南京信息工程大学 | Dual-polarization receiving gas detection laser radar and gas detection method |
| CN115290599A (en) * | 2022-10-08 | 2022-11-04 | 青岛镭测创芯科技有限公司 | Laser radar system for measuring concentration of greenhouse gas |
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