CN211627368U - Gas concentration remote sensing detection device based on coherent detection method - Google Patents
Gas concentration remote sensing detection device based on coherent detection method Download PDFInfo
- Publication number
- CN211627368U CN211627368U CN202020081794.XU CN202020081794U CN211627368U CN 211627368 U CN211627368 U CN 211627368U CN 202020081794 U CN202020081794 U CN 202020081794U CN 211627368 U CN211627368 U CN 211627368U
- Authority
- CN
- China
- Prior art keywords
- light
- imaging lens
- signal
- laser
- gas concentration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 46
- 230000001427 coherent effect Effects 0.000 title claims abstract description 21
- 238000003384 imaging method Methods 0.000 claims abstract description 39
- 238000010521 absorption reaction Methods 0.000 claims abstract description 27
- 230000035559 beat frequency Effects 0.000 claims abstract description 10
- 230000010355 oscillation Effects 0.000 claims abstract description 8
- 230000035945 sensitivity Effects 0.000 abstract description 6
- 239000007789 gas Substances 0.000 description 43
- 238000000034 method Methods 0.000 description 14
- 238000005259 measurement Methods 0.000 description 8
- 238000000041 tunable diode laser absorption spectroscopy Methods 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 241000282414 Homo sapiens Species 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000000862 absorption spectrum Methods 0.000 description 2
- 230000004083 survival effect Effects 0.000 description 2
- 238000004847 absorption spectroscopy Methods 0.000 description 1
- 238000012271 agricultural production Methods 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 235000013405 beer Nutrition 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000001285 laser absorption spectroscopy Methods 0.000 description 1
- 238000001307 laser spectroscopy Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Images
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The utility model belongs to the technical field of laser technology uses, a gas concentration remote sensing detection device based on coherent detection method is provided. A frequency modulation laser beam emitted by the tunable laser is collimated by the laser collimating device and then divided into two paths of light by the first light splitter. One path is signal light, and the other path is local oscillation light. The signal light is irradiated on the target wall surface and is used for detecting the gas to be detected. The signal light scattered by the wall surface sequentially passes through the plurality of imaging lenses and the second light splitting sheet, and beat frequency coherence is generated between the signal light and local oscillation light reflected by the second light splitting sheet. The beat frequency coherent signal is received by a photoelectric detector and finally collected by a data acquisition card, and the computer module is used for inverting the concentration of the gas to be detected. The utility model is suitable for a detection of weak light signal has higher sensitivity and SNR, can realize the simultaneous detection of absorption distance and absorption signal intensity.
Description
Technical Field
The utility model belongs to the technical field of laser spectroscopy technique is used, concretely relates to gas concentration remote sensing detection device based on coherent detection method.
Background
The atmospheric environment is closely related to human survival, and almost every factor of the atmospheric environment affects the survival and development of human beings. Atmospheric pollution not only poses great threat to human health, but also affects global climate change and causes serious harm to ecosystem and industrial and agricultural production, and the measurement of atmospheric pollution gas concentration by utilizing an advanced optical remote sensing detection technology has great significance to atmospheric environment monitoring and treatment. The traditional gas concentration remote sensing detection technology mainly comprises a differential absorption spectroscopy (DOAS) technology, a differential absorption lidar (DIAL) technology, a hard target Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology and the like.
The DOAS technique is a method of detecting by using the difference between the absorption spectra of gas on and off the absorption line (prior art [1 ]: Scante Wallin, "DOAS method is implemented in continuous emission of pollution sources and in-line monitoring of process gas", proceedings of environmental engineering, 2011). And obtaining the concentration information of the gas to be detected by carrying out inversion according to the Belronbo theorem through the differential absorption characteristics of the gas to be detected on the corresponding wave band. The DOAS method can be used for measuring the concentrations of various gas molecules on a laser beam path, does not influence the chemical characteristics of the measured gas, and has the advantages of quick response and no need of pretreatment. When the DOAS technology is used for carrying out gas concentration remote sensing detection, a light beam is generally wide in spectrum (such as a xenon lamp and the like), a reflector needs to be placed at the far end, and therefore light signals are reflected back to a system for photoelectric detection (a spectrometer is generally used), and finally the average gas concentration on a laser path can be measured. In practical application, the method is only suitable for gas concentration remote sensing detection of a fixed scene (or path), and mobile outdoor remote sensing detection is difficult to realize.
The differential absorption laser radar (DIAL) technology (prior art [2]: Liang Mei, et al., "differential absorption laser system applied for background mechanical calibration in South China", Optics and Lasers in Engineering,2014) is an active optical remote sensing technology, and has the characteristics of high spatial resolution, high detection sensitivity, large measurement range and the like. The DIAL technique is based on the principle that laser pulses with different wavelengths (one wavelength is located at an absorption peak of a gas to be measured, and the other wavelength deviates from the absorption peak of the gas to be measured) are alternately emitted into the atmosphere, simultaneously, atmosphere backscatter signals of the two wavelengths are detected by using a high-sensitivity detector (such as a photomultiplier tube) and the concentration of the gas to be measured at different distances is solved according to the difference (ratio) of the absorption intensity of the atmosphere echo signals of the gas to be measured to the two wavelengths. However, in order to realize remote sensing of gas concentration at different distances, the DIAL technique requires the use of a nanosecond-level tunable high-energy pulsed laser light source, which results in an extremely complex system, requires frequent maintenance during measurement, and cannot continuously and stably measure for a long time, thus greatly limiting the practical application of the technique.
Hard-target tunable semiconductor laser absorption spectroscopy (TDLAS) (prior art [3 ]: Jeremy t. dome, et al, 'demodulation of spatial green house gas mapping using laser absorption spectra on local scales', Journal of Applied Remote Sensing,2017) is based on narrow-linewidth semiconductor laser technology and beer lambert law. Under the conditions of controlling temperature and changing driving current, the wavelength of laser output by the laser is tuned, the laser wavelength is scanned near a gas absorption spectral line, and then the detection of the gas concentration is completed by measuring the intensity of an optical signal of the laser absorbed by the gas. When the TDLAS technique is used to perform remote sensing detection of gas concentration, a narrow-linewidth (10MHz) laser beam is generally subjected to wavelength (or frequency tuning) and then transmitted to a remote hard target, such as a building. The emitted light signal is absorbed by the gas to be detected and reflected back to the detection system by the hard target, and is directly detected by the photoelectric detector, and finally the average concentration of the gas to be detected on the laser path can be obtained according to the intensity and the absorption path of the absorption signal. The distance between the hard target and the system is typically obtained by laser rangefinder measurements. The hard target TDLAS technology is relatively simple, easy to realize and good in stability. However, because the power of the narrow-linewidth semiconductor laser used is generally small, when the laser beam is emitted to a hard target for remote sensing detection, the scattered light signal received by the detector is very weak, so that the system is limited to night short-distance remote sensing detection only. Under the condition of strong background light in the daytime, the system is seriously interfered by background light noise, the detection sensitivity is low, and the remote sensing detection of the atmospheric gas concentration is difficult to realize.
In conclusion, how to realize a gas concentration remote sensing detection technology with convenient outdoor measurement, low cost, good stability and high sensitivity is one of important subjects in the field of atmospheric environment monitoring.
SUMMERY OF THE UTILITY MODEL
The utility model provides a gas concentration remote sensing detection technology based on coherent detection method effectively overcomes application bottleneck problems such as traditional gas concentration remote sensing detection technology system complicacy, poor stability, sensitivity are not high, mobility is poor.
The technical scheme of the utility model:
a gas concentration remote sensing detection device based on a coherent detection method comprises a signal generator 1, a DFB laser 2, a first imaging lens 3, a first light splitter 4, a second imaging lens 6, an aperture diaphragm 7, a third imaging lens 8, a first reflector 9, a second reflector 10, a second light splitter 11, a photoelectric detector 12, a data acquisition card 13 and a computer 14;
the sawtooth signal generated by the signal generator 1 is loaded on the DFB laser 2 to modulate the frequency or wavelength of the DFB laser 2; the laser beam from the DFB laser 2 is collimated by a first imaging lens 3. The collimated light is split into two lights by the first dichroic sheet 4. One path of light is reflected to the hard target 5 through the first light splitter 4 as signal light; the other path of light is transmitted through the first light splitter 4 as local oscillator light. The signal light is scattered by the hard target 5, and the obtained scattered light signal is changed into parallel light after sequentially passing through the second imaging lens 6, the aperture diaphragm 7 and the third imaging lens 8; the aperture diaphragm 7 is positioned at the back focal length of the second imaging lens 6; the distance between the diaphragm 7 and the third imaging lens 8 is the front focal length of the third imaging lens 8; the collimated parallel light passes through the second dichroic sheet 11; the local oscillation light is reflected by the first reflecting mirror 9, the second reflecting mirror 10 and the second light splitting sheet 11, meets with the parallel light and interferes; the coherent light is received by the photodetector 12; the photodetector 12 detects a beat frequency signal, and an output end thereof is connected with a signal acquisition input end of the data acquisition card 13.
The DFB laser 2 comprises a DFB laser chip, a current drive and temperature control device, wherein the working wavelength of the DFB laser chip is located near the absorption peak of the gas to be detected, and the line width is superior to 10 MHz.
The laser emitted by the DFB laser 2 is a frequency modulation laser beam.
The splitting ratio of the first light splitter 4 is 90:10, wherein the end outputting the signal light is 90% light, and the end outputting the local oscillator light is 10% light.
The splitting ratio of the second dichroic sheet 11 is 50: 50.
The focal length of the first imaging lens 3 is 15mm, and the caliber of the first imaging lens is 12.7 mm;
the focal length of the second imaging lens 6 is 175mm, and the aperture is 50 mm;
the focal length of the third imaging lens 8 is 15mm, and the aperture is 12.7 mm.
The utility model has the advantages that:
the utility model discloses gas concentration remote sensing detection device based on coherent detection method adopts the harmonious narrow linewidth semiconductor laser of frequency (or wavelength) as the light source to divide into local oscillator light sum signal light. The signal light is emitted to the hard target, scattered by the hard target and collected by the lens. By utilizing the coherent detection of the photoelectric detector, the generated beat frequency signal can realize the distance detection of a hard target on one hand and the detection of the absorption signal of the concentration of the gas to be detected on the other hand. According to the absorption signal intensity and the distance, the average concentration of the gas to be measured on the measuring path can be obtained. The method has the following advantages:
(1) by means of coherent detection, not only background light can be effectively inhibited, but also optical amplification of signal light can be achieved by using local oscillator light with high intensity, and therefore signal-to-noise ratio and detection sensitivity are greatly improved.
(2) The beat frequency is directly related to the absorption range, and the absorption range can be directly calculated, so that the absorption range does not need to be measured by other technical means, and the outdoor mobile measurement is convenient.
Drawings
Fig. 1 is an apparatus diagram of a gas concentration remote sensing system based on a coherent detection method.
Fig. 2 is a graph of laser output frequency.
Fig. 3 is a beat signal diagram.
Fig. 4 is a diagram of a beat signal spectrum.
Fig. 5 is a graph of absorption signals.
In the figure: 1 a signal generator; a 2DFB laser; 3 a first imaging lens; 4 a first light-splitting sheet; 5, a hard target; 6 a second imaging lens; 7, a diaphragm; 8 a third imaging lens; 9 a first mirror; 10 a second mirror; 11 a second dichroic sheet; 12 a photodetector; 13 a data acquisition card; 14 computer.
Detailed Description
The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.
A gas concentration remote sensing detection method based on coherent detection method, this method specifically is:
A. the signal generator 1 generates a sawtooth wave which is transmitted to the drive of the DFB laser 2, causing the DFB laser 2 to emit a frequency modulated laser beam. Meanwhile, the data acquisition card 13 receives the trigger signal and prepares to start data acquisition. The frequency modulation period of the laser is T(s), and the frequency modulation range is delta v (m).
B. The frequency modulated laser beam is collimated by the first imaging lens 3, the collimated light is divided into two paths of light by the first light splitter 4 according to a ratio of 90:10, wherein 90% of the collimated light is signal light, and 10% of the collimated light is local oscillation light. The signal light is reflected by the first light splitting sheet 4, passes through the target gas, and then reaches the hard target 5. And the other path of light is transmitted through the first light splitter and is used as local oscillation light.
C. After being scattered by the hard target 5, the signal light is received and collimated into parallel light by the second imaging lens 6, the aperture stop 7 and the third imaging lens 8, and the parallel light is transmitted through the second dichroic plate 11.
D. The local oscillation light is coherent with the collimated parallel light after being reflected by the first reflecting mirror 9 and the second reflecting mirror 10 and reflected by the second light splitting sheet 11.
E. The resulting coherent light is received by photodetector 12.
F. The photodetector 12 transmits the received beat frequency signal to the data acquisition card 13 for acquisition.
G. The computer 14 performs Fourier transform on the beat frequency signals acquired by the data acquisition card 13. On the frequency domain signal, the size f of the beat frequency signal frequency can be obtainedb. In the case of the known light speed c, the absorption path L of the gas to be measured can be calculated according to the following formula:
H. windowing is performed on the frequency domain signal, and only the frequency spectrum near the beat frequency signal is reserved. The signal is subjected to inverse Fourier transform, and the absorption signal S of the gas to be measured can be obtainedabs. Assuming a known gas concentration of CrefAbsorption range is LrefThe gas absorption signal intensity under the condition is Sref(generally obtained by calibration experiments with known concentrations and absorption paths). The average concentration of the gas in the laser measurement path can be expressed as:
I. the system is aligned to any hard target 5, laser beams are emitted, the intensity of scattered light signals is detected, and the average concentration of the gas on the path to be measured can be obtained according to the method, so that the mobile (or any path) gas concentration measurement is realized.
The above description is further detailed in connection with the preferred embodiments of the present invention, and it is not to be construed that the specific embodiments of the present invention are limited to these descriptions. To the utility model belongs to the technical field of the ordinary technical personnel, do not deviate from the utility model discloses a under the prerequisite of the design, can also make simple deduction and replacement, all should regard as the utility model discloses a protection scope.
Claims (5)
1. A gas concentration remote sensing detection device based on a coherent detection method is characterized by comprising a signal generator (1), a DFB laser (2), a first imaging lens (3), a first light splitting sheet (4), a second imaging lens (6), an aperture diaphragm (7), a third imaging lens (8), a first reflector (9), a second reflector (10), a second light splitting sheet (11), a photoelectric detector (12), a data acquisition card (13) and a computer (14);
the sawtooth signal generated by the signal generator (1) is loaded on the DFB laser (2), frequency or wavelength modulation is carried out on the DFB laser (2), and the driving and temperature control of the DFB laser (2) are controlled, so that the wavelength of a laser beam only has one gas absorption peak in a linear output range; the laser beam from the DFB laser (2) is collimated into parallel light by a first imaging lens (3); the parallel light is divided into two paths of light through a first light splitter (4): one path of light is reflected to a hard target (5) through a first light splitting sheet (4) as signal light; the other path of light is transmitted through the first light splitting sheet (4) and is used as local oscillation light; the signal light is scattered by a hard target (5), and the obtained scattered light signal is changed into parallel light after sequentially passing through a second imaging lens (6), an aperture diaphragm (7) and a third imaging lens (8); the aperture diaphragm (7) is positioned at the back focal length of the second imaging lens (6); the distance between the diaphragm (7) and the third imaging lens (8) is the front focal length of the third imaging lens (8); the collimated parallel light is transmitted through a second light-splitting sheet (11); the local oscillation light meets and interferes with the parallel light after being reflected by the first reflecting mirror (9), the second reflecting mirror (10) and the second light splitting sheet (11) in sequence; the generated coherent light is received by a photodetector (12); the photoelectric detector (12) detects beat frequency signals, and the output end of the photoelectric detector is connected with the signal acquisition input end of the data acquisition card (13).
2. The remote gas concentration sensing device based on the coherent detection method according to claim 1, wherein the laser emitted by the DFB laser (2) is a frequency modulated laser beam, and comprises a DFB laser chip and a current driving and temperature control device, the working wavelength of the DFB laser (2) chip is located near the absorption peak of the gas to be detected, and the line width is better than 10 MHz.
3. The remote sensing device for gas concentration based on coherent detection method according to claim 1 or 2, wherein the splitting ratio of the first light splitter (4) is 90:10, wherein the signal light accounts for 90% and the local oscillator light accounts for 10%.
4. The remote gas concentration sensing device based on the coherent detection method according to claim 1 or 2, wherein:
the focal length of the first imaging lens (3) is 15mm, and the caliber of the first imaging lens is 12.7 mm;
the focal length of the second imaging lens (6) is 175mm, and the aperture is 50 mm;
the focal length of the third imaging lens (8) is 15mm, and the caliber of the third imaging lens is 12.7 mm.
5. The remote gas concentration sensing device based on the coherent detection method according to claim 3, wherein:
the focal length of the first imaging lens (3) is 15mm, and the caliber of the first imaging lens is 12.7 mm;
the focal length of the second imaging lens (6) is 175mm, and the aperture is 50 mm;
the focal length of the third imaging lens (8) is 15mm, and the caliber of the third imaging lens is 12.7 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020081794.XU CN211627368U (en) | 2020-01-15 | 2020-01-15 | Gas concentration remote sensing detection device based on coherent detection method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020081794.XU CN211627368U (en) | 2020-01-15 | 2020-01-15 | Gas concentration remote sensing detection device based on coherent detection method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN211627368U true CN211627368U (en) | 2020-10-02 |
Family
ID=72637924
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020081794.XU Active CN211627368U (en) | 2020-01-15 | 2020-01-15 | Gas concentration remote sensing detection device based on coherent detection method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN211627368U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111122500A (en) * | 2020-01-15 | 2020-05-08 | 大连理工大学 | Gas concentration remote sensing detection device and method based on coherent detection method |
-
2020
- 2020-01-15 CN CN202020081794.XU patent/CN211627368U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111122500A (en) * | 2020-01-15 | 2020-05-08 | 大连理工大学 | Gas concentration remote sensing detection device and method based on coherent detection method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111122500A (en) | Gas concentration remote sensing detection device and method based on coherent detection method | |
| US11397149B2 (en) | Laser radar system apparatus for multi-wavelength measurement of atmospheric carbon dioxide concentration and vertical aerosol profile | |
| CN110749872A (en) | Coherent differential absorption laser radar and method for detecting gas concentration | |
| US7349094B2 (en) | Laser radar apparatus having multiple output wavelengths | |
| CN111208084A (en) | Optical fiber gas concentration remote sensing detection device and method based on coherent detection method | |
| US20220026577A1 (en) | Dispersion gating-based atmospheric composition measurement laser radar | |
| CN111398991B (en) | Quantum cascade laser differential absorption laser radar VOCs concentration detection method | |
| CN211528208U (en) | Optical fiber gas concentration remote sensing detection device based on coherent detection method | |
| CN114384045B (en) | Trace gas concentration and path length real-time detection system and method | |
| CN109580541B (en) | Optical heterodyne cavity ring-down spectroscopy measurement device and method | |
| CN107219199A (en) | Novel angle modulation SPR imaging systems based on 4F systems | |
| CN105823755A (en) | Self-mixing gas absorption sensing system based on tunable semiconductor laser | |
| CN1641377A (en) | Incoherent laser windfinding method and laser radar | |
| KR20240090336A (en) | System and method for simultaneous high-sensitivity measurement of methane and ethane via laser absorption spectroscopy in open-air configuration | |
| CN211627368U (en) | Gas concentration remote sensing detection device based on coherent detection method | |
| CN109375190B (en) | Frequency comb laser radar detection method and system for simultaneously measuring multiple atmospheric components | |
| CN214151058U (en) | Dual-beam laser radar wind field detection device | |
| CN112986965B (en) | Real-time calibration device for differential cross section of water vapor differential absorption laser radar | |
| CN114813648A (en) | Heterodyne detection spontaneous Rayleigh Brillouin scattering spectrum method and device | |
| CA2997148C (en) | Laser gas analyzer | |
| US11391667B2 (en) | Laser gas analyzer | |
| JPH08247940A (en) | Road surface state detection device | |
| CN109343080B (en) | Method for detecting water vapor by Raman laser radar adopting heterodyne technology and radar system | |
| CN111693460A (en) | Detection apparatus based on polarized light beam saturated absorption spectrum | |
| EP4283341A1 (en) | Lidar device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |