CN208013060U - A kind of more gas detecting systems of wave-length coverage and wavelength continuously adjustable - Google Patents
A kind of more gas detecting systems of wave-length coverage and wavelength continuously adjustable Download PDFInfo
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Abstract
More gas detecting systems of a kind of wave-length coverage and wavelength continuously adjustable, including optical fiber laser, acousto-optic modulator, collimator, gas absorption cell, photodetector, spectral signal analysis module, Laser Driven control module and radiofrequency drive system；Optical fiber laser, acousto-optic modulator, collimator, gas absorption cell and photodetector are set gradually；Optical fiber laser is connect with the output end of Laser Driven control module, and photodetector is connected with spectral information analysis module；Radiofrequency drive system is connect with acousto-optic modulator and spectral signal analysis module；Acousto-optic modulator is generated with frequency synthesizer, and frequency synthesizer is connect with the microprocessor in spectral signal analysis module.The network analysis speed is fast；Conversion speed is fast；Detect optical maser wavelength continuously-tuning；Can real-time online detection, also can teletransmission analysis monitoring；It is good to detect stability, accuracy；Cost is low, it is only necessary to which the detection of majority of gas ingredient can be completed in a tunable laser.
Description
Technical field
The utility model is related to a kind of systems for multiple gases detection, using a kind of wave-length coverage continuously-tuning light
Fibre laser and fiber coupling acousto-optic modulator composite structure realize the more gas detections of wavelength continuously-tuning, belong to laser gas
Body detection technique field.
Background technology
Field is absorbed in gaseous spectrum, tunable diode laser absorption spectroscopy analyzes (Tunable diode laser
Absorption spectroscopy, TDLAS) it is a kind of highly sensitive, high-resolution and quick response gas detection skill
Art is widely used in the fields such as gas monitor, ambient air detection and the scientific research in industrial flow.
When the concentration to multiple gases ingredient is detected, it is intended to that the spectrum of multiple gases ingredient can be measured simultaneously
Absorption Line.The shortcomings that existing infrared tuned laser is that tuning range is limited, generally in 200cm-1Magnitude, fast current tune
Humorous width about 1-2cm-1, in actual gaseous detection applications, usually realized to detection gas spectrum by electric current tuning mode
Absorption Line is used for quickly detecting, still, smaller in the tuning range of existing tunable laser, generally can not cover all gas
The optical maser wavelength that body absorbs；And since thermal tuning cannot achieve quick tuning, by noise spectra of semiconductor lasers into trip temperature tune
When humorous method realizes the detection to a plurality of spectral absorption line, the used time is longer.In practical application, generally requires and need to examine for each
With the frequency multiplexing technique to work, the frequency multiplexing technique currently used for multi-analyte immunoassay technology can be divided into three kinds, be respectively the gas of survey
Time-division multiplex technology, wavelength division multiplex technology and frequency-division modulation frequency multiplexing technique.
Time-division multiplex technology is most straightforward approach, it is that corresponding measurement gas pair is selected from a series of laser
The measuring beam of wavelength is answered to imported into light path, the concentration of sequence detection multiple gases；Wavelength division multiplex technology is by different waves
Long laser beam is combined by wavelength division multiplexer or optical-fiber bundling device, and the multiple beam after combination is logical along identical light path
Absorption cell is crossed, preliminary design light beam is divided using Dichroic Optical Elements, and the light beam of different wave length is connect in different directions by detector
It receives, is detected while realizing more grouping gases；Frequency modulation technique is exactly the narrow-band filtering feature using phase-sensitive detection, is swashed to more
The sinusoidal current signal of light device different frequency is modulated, and laser beam is then carried out conjunction beam, passes through gas along identical light path
Body absorption cell finally focuses on same detector.Again by being demodulated in corresponding frequency to signal, you can from conjunction beam
The contribution that volume isolates each long wavelength laser is extracted in signal, and the concentration of gas componant is corresponded to analyze it.
Wavelength division multiplex technology solves the problems, such as that the detection speed of multicomponent gas while detection is slow, but practical such method
It is not improved much compared with mostly set instrument detecting system, has only shared a gas absorption cell and detection route
.Moreover, bundling device or wavelength division multiplexer and the beam splitter of separation also reduce the compact and stability of system, diffraction
The use of element is also possible to introduce noise and deviation.Main problem existing for frequency-division modulation frequency multiplexing technique is to need to eliminate to detect to lead to
It is restricted on cross jamming and multi-path laser number between road.Compared to both the above method, time-division multiplex technology is detecting
Very simple in system structure, it is only necessary to which a detector, a set of detection device and a set of signal processing system, detection gas are more
Also there is no limit for number of components.But traditional time division frequency multiplexing technique is the conversion that mechanical structure carries out beam light source mostly, this is just
Its efficiency measured is set to be greatly reduced, and such method keeps the stability of light intensity poor.Moreover, traditional time-division multiplex technology because
The multicomponent gas concentration at certain moment can not continuously, be fast and accurately detected for the limitation of lasing light emitter.
The detection of gas with multiple constituents technology mostly used greatly now (is divided by the different Distributed Feedback Laser of several centre wavelengths
Cloth feedback laser) combined multi-wavelength light source is constituted, by the multi-way detecting laser of combined multi-wavelength light source transmitting through wave
After division multiplexer or optical-fiber bundling device close beam, beam detection laser will be closed by multimode fibre before pond and propagated from light inlet and import dress
Have in the gas absorption cell of detected gas, closes beam detection laser and penetrated from light-emitting window after multiple reflections in gas absorption cell
Go out, then by multimode fibre guide probe behind pond, various gas absorption spectrum line optical signals are converted to electric signal by detector, are passed through
The operation of preamplifier and lock-in amplifier obtains the primary and secondary harmonic wave of gas absorption signal, finally utilizes harmonic wave strong
Degree realizes the measurement of gas concentration.
Above-mentioned existing more gas detection technologies utilize identical principle mostly, utilize wavelength division multiplexer or optical-fiber bundling device
Multi-pass is coupled into a single multimode fibre, which, which leads to gas absorption cell, carries out multiwavelength laser while absorbing inspection
It surveys.
However, the above method is when realizing that more gases detect simultaneously, there are following several defects：
After 1. multichannel different wave length detects laser by wavelength division multiplexer, different degrees of decaying can all occur, moreover, by
The laser beam number that the wavelength of coupling is different is more, and decaying is also more serious；
2. for a laser light source more than simultaneously in use, occupancy volume is larger, the requirement to detection environment is more harsh；
3. being affected by environment temperature, the wavelength of semiconductor laser output laser is also influenced by temperature, and can be made
At certain error；
4. detect optical maser wavelength it is discontinuous, on the basis of not changing apparatus components, detectable gas is fixed, instrument can
Transplantability is poor.
Utility model content
The utility model provides a kind of simple in structure, adaptation for deficiency existing for existing more gas composition detection techniques
More gases of complicated measuring environment, gas detection high sensitivity and the strong wave-length coverage and wavelength continuously adjustable of flexibility are examined
Examining system.
The wave-length coverage of the utility model and more gas detecting systems of wavelength continuously adjustable, using following technical side
Case：
The system, including optical fiber laser, acousto-optic modulator, collimator, gas absorption cell, photodetector, spectrum letter
Number analysis module, Laser Driven control module and radiofrequency drive system；Optical fiber laser, acousto-optic modulator, collimator, gas are inhaled
Receives pond and photodetector are set gradually；Optical fiber laser is connect with the output end of Laser Driven control module, photodetector
It is connected with spectral information analysis module；Radiofrequency drive system is connect with acousto-optic modulator and spectral signal analysis module；Acousto-optic tune
Device processed is generated with frequency synthesizer, and frequency synthesizer is connect with the microprocessor in spectral signal analysis module.
The laser wavelength range that Laser Driven control module control optical fiber laser is sent out, the laser that optical fiber laser is sent out
It is modulated into the corresponding wavelength of gas componant by acousto-optic modulator, then collimator imports gas absorption cell, then is visited by laser
It surveys device to receive, the optical signal of receiving is converted into electric signal and gives electric signal transmission to spectral information analysis mould by laser detector
Block, spectral analysis module carry out analyzing processing to the electric signal of receiving, obtain with the relevant electric signal of gas concentration, table is come with this
Levy the concentration information of various component gases in gas absorption cell.
The optical fiber laser is wave-length coverage tunable laser.
The Laser Driven control module includes control scanning circuit, constant-temperature circuit and protection circuit, controls scanning circuit
The wavelength of output laser is set to be scanned in wave-length coverage, temperature control circuit is used for the temperature of stable laser, excludes temperature to output
The influence of the wavelength of laser.
Light path is adjusted in the gas absorption cell, is equipped with air inlet and gas outlet.
The spectral signal analysis module include sequentially connected preamplifier, lock-in amplifier, analog-digital converter and
Microprocessor.
More gas detecting systems of the utility model, further include terminal device, spectral signal analysis module by wired or
Gas concentration data are transmitted to terminal device by wireless mode at a distance.
The utility model is using the continuously adjustable laser light source combination acousto-optic modulator of quick wave-length coverage to detection
The wavelength of laser is adjusted, you can realize wide range of wavelengths continuously adjustable, to realize to most gas componant into
The purpose of row detection.Wavelength regulation can continuity and super wide range impart the extremely strong flexibility of this detecting system with it is removable
Plant property, is suitable for the detection of nearly all component gas.
The utility model proposes acousto-optic modulation technology light-dividing principle compared with other light splitting technologies, have resolution ratio
Height, all solidstate device is secured, is divided the advantages that rapid and arbitrary wavelength switches.The advantages of the utility model, is mainly reflected in：
1. detecting laser wavelength range continuously-tuning, most of gas corresponding wavelength is covered；
2. high resolution, all solidstate device is secured, is divided rapid and arbitrary wavelength switching
3. carrying out wavelength selection using AOTF technologies, wavelength can be selected arbitrarily, spectral scan speed is fast；
4. a light path of the same gas chamber of time-sharing multiplex same light source can not only reduce equipment instrument, movable member is reduced,
The complexity of system is reduced, realization preferably automatically controls；.
5. can real-time online detection, also can teletransmission analysis monitoring；
6. it is good to detect stability, accuracy, the influence of temperature is avoided；
7. cost is low, quantity of light source is reduced, gas chamber design and light path is simplified, reduces the volume of analyzer, drop
The low consumption of sample gas and the energy expenditure of temperature control system.
Description of the drawings
Fig. 1 is the schematic diagram of more gas detecting systems of the utility model wave-length coverage and wavelength continuously adjustable.
In figure：1. spectral signal analysis module, 2. radiofrequency drive systems, 3. Laser Driven control modules, 4. optical-fiber lasers
Device, 5. acousto-optic modulators (AOTF), 6. collimators (collimation lens), 7. gas absorption cells, 8. photodetectors, 9. preposition amplifications
Device, 10. lock-in amplifiers, 11. digital analog converters, 12. control scanning circuits, 13. constant-temperature circuits, 14. protection circuits, 15. is micro-
Processor, 16. frequency synthesizers.
Specific implementation mode
The wave-length coverage of the utility model and more gas detecting systems of wavelength continuously adjustable, as shown in Figure 1, including
Optical fiber laser 4 that wave-length coverage is tunable, acousto-optic modulator 5, collimator 6, gas absorption cell 7, photodetector 8, spectrum
Signal analysis module 1, Laser Driven control module 3 and radiofrequency drive system 2.
Gas absorption cell 7 is equipped with air inlet and gas outlet.The front of gas absorption cell 7 is provided with collimator 6, collimator 6
Front be provided with acousto-optic modulator 5, the front of acousto-optic modulator 5 is provided with optical fiber laser 4, optical fiber laser 4 and laser
Drive control module 3 connects, and acousto-optic modulator 5 is connect with radiofrequency drive system 2, and the rear of gas absorption cell 7 is provided with photoelectricity
Detector 8, photodetector 8 are connect with spectral signal analysis module 1.
Spectral signal analysis module 1 includes sequentially connected preamplifier 10, lock-in amplifier 11, analog-digital converter 12
With microprocessor 15.
Laser Driven control module 3 controls mould for controlling the laser wavelength range that optical fiber laser 4 is sent out, Laser Driven
Block 3 includes control scanning circuit (current scanning circuit) 12, constant-temperature circuit 13 and protection circuit 14, control scanning circuit therein
12 make the wavelength of output laser be scanned in the laser wavelength range sent out.Constant-temperature circuit 13 is used for the temperature of stable laser 4,
Avoid influence of the temperature to the wavelength of output laser.
For the utility model in more gas composition analysis, the critical piece for influencing detection light line frequency is radiofrequency drive system
2, include mainly that channel, power amplifier and RF switch etc. occur for radio frequency.Microprocessor 15 receives control, interpretation host computer
The various orders issued, and order the working condition for controlling entire radiofrequency drive system 2 by executing.Channel occurs for radio frequency
Signal generator, radio-frequency transformer, LC low-pass filters and low-noise amplifier, switch, the frequency of signal generator output signal
Rate and amplitude are controlled by microprocessor 15.It is exported after the filtered amplification of radiofrequency signal, then driving is amplified to by power amplifier
Power bracket needed for acousto-optic modulator 5 selects suitable PZT (piezoelectric transducer) by switching RF switch, radiofrequency signal is loaded
Into AOTF crystal, the control to acousto-optic modulator 5 is completed, the laser of required wavelength is modulated, examined for gas composition concentration
Survey analysis.
The utility model critical piece is acousto-optic modulator (acousto-optic tunable filter, AOTF) 5.5 base of acousto-optic modulator
It is a certain when crystal with Photoelasticity element of the beam of broad spectrum by a high-frequency vibration in the principle of acoustooptical effect
The monochromatic light of wavelength can generate diffraction in crystals, be transmitted from crystal at a certain angle.When the vibration frequency of crystal
When changing, the wavelength of diffraction light also changes correspondingly.In practical applications by the PZT (piezoelectric transducer) of plane of crystal by radio frequency
Signal is converted to the ultrasonic wave of crystals.
Acousto-optic modulator 5 is modulated signal used and is generated by frequency synthesizer 16, frequency synthesizer 16 and microprocessor 15
Connection.The modulating frequency is that absorb infrared light strongest frequency (f1, f2 ... fk) be 5KHz~40KHz to gas.
Frequency, demodulation frequency is nf1, nf2, nf3 ... nfk, preferably n=2, i.e. second harmonic demodulation techniques.
It, can be by following relationship according to Vector modulation relationship：
In formula：
fe→o- incidence e optical diffractions are the RF drive frequency for being emitted o light
fo→e- incidence o optical diffractions are the RF drive frequency for being emitted e light
λ-diffraction wavelength
θi- incident light beam strikes angle
θa- ultrasonic wave incidence angle
noThe refraction angle of (λ)-o light
neThe refractive index of (λ, θ)-e light
va- ultrasonic velocity is determined by AOTF materials
It is derived from AOTF RF drive frequencies and diffraction wavelength tuning relation：
θi- incident angle
θd- angle of diffraction
V-the velocity of sound
ni- about θiFunction
nd- about θdFunction
F-acoustic frequency
λ-vacuum wavelength
As shown from the above formula when AOTF after processing is completed, diffraction wavelength is only controlled by RF drive frequency.Change radio frequency
Driving frequency is the diffraction wavelength of changeable response.
The system of the utility model carries out more gas detections, and details are provided below：
The drive signal that the utility model carries out laser using different modulating frequency (f1, f2 ... fk) is modulated, and
It is demodulated in lock-in amplifier using different frequency, demodulation frequency (nf1, nf2 ... nfk) as with reference to signal.K is k kind gas
Body component.It detects gas with various and uses different modulating frequencies, filter out specific wavelength light through AOTF, then pass through collimator 6
It is collimated, is matched with the optical mode of gas absorption cell 7.
Optical fiber laser 4 is set to carry out the scanning of wavelength in tunable range using length scanning control circuit 12,
The mode of the electric tuning of acousto-optic modulator 5 is recycled to filter out tested gas institute from complicated 4 light source wide spectrum of optical fiber laser
Need the spectrum of wavelength.The light for filtering out gas specific absorption wavelength is interacted with tested gas, light intensity attenuation, and then be irradiated to
On photodetector 8, the photosignal that photodetector 8 is received passes through preamplifier 10,11 and of lock-in amplifier successively
Analog-digital converter 12 carries out preposition amplification filtering and noise reduction and Weak Signal Processing (signal amplifies and analog-to-digital conversion), and then obtains
With the relevant electric signal of gas concentration, the concentration information of various component gases in gas absorption cell is characterized with this.
Microprocessor 15 in spectral signal analysis module 1 is remote by gas concentration data by wired or wireless way
It is transmitted to terminal device, and carries out the frequency modulation(PFM) of next kind of gas componant.
The utility model is using the continuously adjustable laser light source combination acousto-optic modulator of quick wave-length coverage to detection
The wavelength of laser is adjusted, you can realize wide range of wavelengths continuously adjustable, to realize to most gas componant into
The purpose of row detection.Wavelength regulation can continuity and super wide range impart the extremely strong flexibility of this detecting system with it is removable
Plant property, is suitable for the detection of nearly all component gas.
It is loaded into Laser Driven control module 3 with a certain modulating frequency (f1, f2 ... fk), optical path Center is allowed to pass through
Acousto-optic modulator 5 applies electric signal to radiofrequency drive system 2, and control acousto-optic modulator 5 works, i.e. work needed for screening is infrared
Fundamental frequency, outgoing beam are coupled to by collimator 6 in gas absorption cell 7, are incident on photodetector 8 after reflection, will
The photosignal that photodetector 8 receives carries out preposition amplification filtering and noise reduction, and the transmission signal of gained is transmitted to lock-in amplifier
11.According to the overtone order to be detected, lock-in amplifier 11 selects different frequency, demodulation frequency nfk to be demodulated according to modulating frequency.
The ADC converters 12 that signal after demodulation is sent out Jing Guo triple channel are transmitted to microprocessor 15, complete by Embedded algorithm routine
At retrieving concentration, the concentration for completing gas is deduced.When to detect other gas components, by modulating different frequency and screening
The infrared light of different wave length, the same sense channel of time-sharing multiplex carry out the detection of another gas component.
The utility model has the characteristics that：
1. the optical fiber laser cooperation acousto-optic laser using wave-length coverage continuously adjustable provides detection laser, wavelength covers
Lid range is wide, and the type of detectable gas is more；
2. laser light source has temperature control system, so that the temperature of laser light source is maintained at a certain suitable temperature, avoid temperature pair
The influence of spectral wavelength, and the utility model reduces the volume of analyzer, the energy expenditure of temperature control system is reduced, temperature control
Also evenly stablize.
3. the utility model significantly simplifies Optical System Design.A kind of traditional analyte of TDLAS analyzers uses one
Gas chamber or a light path.The utility model uses a light path, and system is reduced also without rotatable parts without multiple light sources
Mechanical complexity；Gas chamber number is saved, gas chamber design is simplified.
4. gas chamber increases light path using multiple reflection principle, to improve the sensitivity of system detectio, more air-exchanging chamber or change
Become air chamber length, it can be achieved that different ranges and sensitivity requirement；
5. system carries out wavelength selection using AOTF technologies, as long as its gas characteristic absorption line selectable waves of AOTF again
It is detectable in long range, it is not directed to a certain fixed gas ingredient, it is portable strong.
6. accelerating the speed of detection；
7. the Weak Signal Processing technology amplified using modulation /demodulation and locking phase, realizing reduces flicker noise (1/f noise)
Effect.
Claims (5)
1. more gas detecting systems of a kind of wave-length coverage and wavelength continuously adjustable, it is characterized in that：Including optical fiber laser,
It acousto-optic modulator, collimator, gas absorption cell, photodetector, spectral signal analysis module, Laser Driven control module and penetrates
Frequency drive system；Optical fiber laser, acousto-optic modulator, collimator, gas absorption cell and photodetector are set gradually；Optical fiber swashs
Light device is connect with the output end of Laser Driven control module, and photodetector is connected with spectral information analysis module；Radio-frequency driven
System is connect with acousto-optic modulator and spectral signal analysis module；Acousto-optic modulator is generated with frequency synthesizer, frequency synthesizer
It is connect with the microprocessor in spectral signal analysis module.
2. more gas detecting systems of wave-length coverage according to claim 1 and wavelength continuously adjustable, it is characterized in that：
The optical fiber laser is wave-length coverage tunable laser.
3. more gas detecting systems of wave-length coverage according to claim 1 and wavelength continuously adjustable, it is characterized in that：
The Laser Driven control module includes control scanning circuit, constant-temperature circuit and protection circuit, and control scanning circuit makes output swash
The wavelength of light scans in wave-length coverage, and temperature control circuit is used for the temperature of stable laser, excludes wave of the temperature to output laser
Long influence.
4. more gas detecting systems of wave-length coverage according to claim 1 and wavelength continuously adjustable, it is characterized in that：
The spectral signal analysis module includes sequentially connected preamplifier, lock-in amplifier, analog-digital converter and microprocessor.
5. more gas detecting systems of wave-length coverage according to any one of claims 1 to 4 and wavelength continuously adjustable,
It is characterized in that：It further include terminal device.
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| CN109211825A (en) * | 2018-10-10 | 2019-01-15 | 吉林大学 | Solution gas infrared detecting device and method in a kind of water using acoustooptical effect collimated light path |
| CN109580585A (en) * | 2019-01-07 | 2019-04-05 | 重庆大学 | Characteristic of transformer gas Raman spectrum detection device and detection method |
| CN109612939A (en) * | 2019-01-24 | 2019-04-12 | 中国科学院长春光学精密机械与物理研究所 | Food deterioration degree-measuring system and detection method based on infrared absorption spectrum |
| CN110160990A (en) * | 2019-05-30 | 2019-08-23 | 深圳华领气体技术有限公司 | Trace gas and its isotope real time on-line detection device |
| CN111948173A (en) * | 2020-08-12 | 2020-11-17 | 电子科技大学 | TDLAS signal processing system based on acousto-optic correlation technique |
| CN113922872A (en) * | 2021-12-14 | 2022-01-11 | 广州汇信特通信技术股份有限公司 | Optical amplitude modulation and demodulation system based on 5G transmission |
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| CN109211825A (en) * | 2018-10-10 | 2019-01-15 | 吉林大学 | Solution gas infrared detecting device and method in a kind of water using acoustooptical effect collimated light path |
| CN109580585A (en) * | 2019-01-07 | 2019-04-05 | 重庆大学 | Characteristic of transformer gas Raman spectrum detection device and detection method |
| CN109580585B (en) * | 2019-01-07 | 2021-07-23 | 重庆大学 | Transformer characteristic gas Raman spectrum detection device and detection method |
| CN109612939A (en) * | 2019-01-24 | 2019-04-12 | 中国科学院长春光学精密机械与物理研究所 | Food deterioration degree-measuring system and detection method based on infrared absorption spectrum |
| CN109612939B (en) * | 2019-01-24 | 2020-08-21 | 中国科学院长春光学精密机械与物理研究所 | Food deterioration degree detection system and detection method based on infrared absorption spectrum |
| CN110160990A (en) * | 2019-05-30 | 2019-08-23 | 深圳华领气体技术有限公司 | Trace gas and its isotope real time on-line detection device |
| CN111948173A (en) * | 2020-08-12 | 2020-11-17 | 电子科技大学 | TDLAS signal processing system based on acousto-optic correlation technique |
| CN113922872A (en) * | 2021-12-14 | 2022-01-11 | 广州汇信特通信技术股份有限公司 | Optical amplitude modulation and demodulation system based on 5G transmission |
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