CN105466854A - Active air-chamber structure and photoacoustic spectrometry gas sensing system - Google Patents
Active air-chamber structure and photoacoustic spectrometry gas sensing system Download PDFInfo
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- CN105466854A CN105466854A CN201511021893.9A CN201511021893A CN105466854A CN 105466854 A CN105466854 A CN 105466854A CN 201511021893 A CN201511021893 A CN 201511021893A CN 105466854 A CN105466854 A CN 105466854A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
Abstract
The invention discloses an active air-chamber structure and photoacoustic spectrometry gas sensing system. The active air-chamber structure and photoacoustic spectrometry gas sensing system comprises an integrated light source, a photoacoustic cell, a microphone, a photoelectric detection module, a signal processing module, a light source control module and a data output module; the integrated light source and one end of the photoacoustic cell are directly packaged into a whole, and the microphone is installed on the side wall of the photoacoustic cell; the photosensitive surface of the photoelectric detection module is aligned to a light emitting port of the photoacoustic cell, the output end of the photoelectric detection module and the output end of the microphone are both connected to the input end of the signal processing module, one output end of the signal processing module is connected with the light source control module, the other output end of the signal processing module is connected with the data output module, and the light source control module is connected with the control end of the integrated light source. According to the active air-chamber structure and photoacoustic spectrometry gas sensing system, the structural design of directly packaging a specially designed DFB semiconductor laser and one end of an air chamber into a whole is adopted, the intermediate link of coupling with optical fibers is omitted, and the injected light power is greatly increased; meanwhile, the light beam adjustment structure is simplified, and air chamber miniaturization and stability improvement are achieved.
Description
Technical field
The present invention relates to a kind of sensing unit structures in field of gas detection and light sensory field, be specifically related to a kind of active air chamber structure and optoacoustic spectroscopy gas sensing system of integrated optical source formula.
Background technology
In recent years, along with maturation and the growth of optical communication industry, the cost of large quantities of high performance optical devices constantly reduces, especially the semiconductor DFB of near infrared communication wave band (800 ~ 1700nm), and its output power and line width characteristic are all greatly improved.Make to realize modern industry and apply the high precision be badly in need of and on-line monitoring becomes possibility.Optoacoustic spectroscopy is a kind of detection technique without background signal, have do not consume gas sample, highly sensitive, detection time is short, be convenient to the advantages such as Site Detection.For the sample gas that concentration is very low, still higher sensitivity can be obtained.Such as, the maturation of near infrared narrow linewidth DFB semiconductor laser, can near infrared communication wave band (800 ~ 1700nm) Distributed Feedback Laser of utility excellence easily, realizes in conjunction with optoacoustic spectroscopy the real-time measurement being better than 1ppm.Although some gas at present, as ethane, there is no obvious absorption at near-infrared band, the volume production of the quanta cascade DFB light source near mid infrared region 3400nm also points the day and await for it, and provides another power-assisted for these gases realize highly sensitive detection.
Present stage, the detection of ppm level trace characteristic gas concentration mainly adopts vapor-phase chromatography.The Standard Operating Procedure of vapor-phase chromatography comprises: on-the-spot oil sample collection, and---electrochemical process completes Concentration Testing to laboratory gas-oil separation---chromatographic column realizes gas composition separation (solving the cross sensitivity problem of electrochemical method) excessively---.This detection mode complex operation, the cycle is long and chromatographic column belongs to consumptive material needs periodic replacement., as semiconductor gas sensor and FTIR spectrum technology, all there is sensitivity or lack the defects such as real-time, therefore extensively cannot drop into commercial Application in other detection methods.
Optoacoustic spectroscopy gas detection technology has the advantages such as highly sensitive (laboratory single gas detect precision reach ppt magnitude), real-time are good, has great development potentiality at industrial circle.In early stage optoacoustic spectroscopy R&D process, we find its core---the structural design of photo acoustic gas cell plays decisive role to the sensitivity promoting photo-acoustic detection system, stability and miniaturized structure with optimizing.Under the prerequisite ensureing system sensitivity, the miniaturization of photo acoustic gas cell reduces the primary concern detecting air consumption, improve response speed.And little resonant cavity (diameter ~ 2mm) needs the guarantee of Laser Output Beam diameter and technique for fixing (light beam is parallel with resonator axis), and meet the requirement of resonator cavity inwall machining precision, and the structure that Distributed Feedback Laser more common at present+optical fiber collimator exports, higher requirement is proposed to light beam parallelism and collimated process thereof, limits the miniaturization of air chamber.
Summary of the invention
The technical problem to be solved in the present invention is, the problem of the light source couples existed for existing air chamber/gas cell and light beam adjusting process complexity, poor stability, a kind of active air chamber structure and optoacoustic spectroscopy gas sensing system of integrated optical source formula are provided, greatly improve injected optical power, simplify light beam adjust structure simultaneously, realize the raising of air chamber miniaturization and stability.
The present invention for solving the problems of the technologies described above adopted technical scheme is:
A kind of active air chamber structure and optoacoustic spectroscopy gas sensing system, it comprises integrated optical source, photoacoustic cell, microphone, photoelectric detection module, signal processing module, light source control module and data outputting module, described integrated optical source one end that is direct and photoacoustic cell is packaged as a whole and forms overall photo acoustic gas cell, described microphone be arranged on photoacoustic cell outside, for detecting the intensity of the sound pressure signal formed in photoacoustic cell, and be translated into electric signal; The photosurface of described photoelectric detection module aim at photoacoustic cell bright dipping end, for light signal is converted into electric signal; The output terminal of photoelectric detection module and microphone is all connected to the input end of signal processing module, and an output terminal of signal processing module is connected with light source control module, another output terminal is connected with data outputting module; Described light source control module is connected with the control end of integrated optical source.
By such scheme, described integrated optical source adopts near infrared DFB semiconductor laser.
By such scheme, described photo acoustic gas cell is single port or two-port air chamber (without emergent light monitoring under single port, having emergent light to monitor under dual-port).
By such scheme, described signal processing module comprises lock-in amplifier, and signal processing module utilizes phase locking technique to realize weak signal by lock-in amplifier and extracts.
Principle of work of the present invention: one end that the is integrated optical source (Distributed Feedback Laser) improved is direct and photoacoustic cell is encapsulated into one, makes photoacoustic cell and integrated optical source become an Integral air chamber structure; Light source control module is connected with integrated optical source control end, utilizes the generation of semiconductor laser frequency modulation technology have the exciting light of acoustics modulation signature and be directly injected in photoacoustic cell; Be stimulated after specific gas molecule absorption luminous energy in photo acoustic gas cell, transit to the high-energy state of vibrational energy level, and then be kinetic energy by radiationless transition by Conversion of Energy, thus in photoacoustic cell mineralization pressure ripple; Utilize microphone to detect the intensity of the pressure wave signal formed in photoacoustic cell, and be translated into electric signal; Light signal is changed into electric signal by photoelectric detection module; Signal processing module receives the electric signal of microphone output terminal and the electric signal of photoelectric detection module output terminal, and carries out filter amplifying processing to the electric signal received; An output terminal of signal processing module is connected with light source control module, utilizes output signal to carry out negative feedback to light source control module, thus guarantees integrated optical source stable output; Another output terminal of signal processing module by interface circuit by Signal transmissions to data outputting module, carry out data processing and display.According to the relation of sound pressure signal amplitude and incident intensity, gas molecules sorb coefficient and content, thus the molecule content of gas of determining to be stimulated in photo acoustic gas cell, finally obtain gas concentration to be measured.
Compared with the optoacoustic spectroscopy detection method of other types, the present invention has following advantages and good effect:
1, start with from illuminating source packaging structure, devise a kind of integrated optical source formula air chamber structure, by DFB semiconductor laser directly and the project organization that is integrated of photo acoustic gas cell one end encapsulation and integration, eliminate optical fiber collimator, optimize the light injecting structure design of air chamber---improve the angle of divergence injecting light beam, reduce beam divergence, improve the luminous power and structural stability of injecting air chamber, be finally achieved the further miniaturization of photo acoustic gas cell volume;
2, semiconductor laser frequency modulation technology is the resonant operational state for realizing photo acoustic gas cell, light source frequency is modulated, make the resonance frequency matches of light source frequency and photo acoustic gas cell, thus obtain maximum output signal, and with the gas sensing system that this air chamber is core, achieve the acetylene gas accuracy of detection being better than 0.5ppm;
3, because photoacoustic signal is the AC signal with modulation of source frequency cross-correlation, therefore utilize phase locking technique to suppress uncorrelated noise in data handling procedure, thus improve the signal to noise ratio (S/N ratio) of system, also facilitate the phase place extracting photoacoustic signal and frequency simultaneously.
Accompanying drawing explanation
Fig. 1 is the structure principle chart of the active air chamber structure of the present invention and optoacoustic spectroscopy gas sensing system;
In figure, 1-near infrared DFB semiconductor laser, 2-photoacoustic cell, 3-microphone, 4-photoelectric detection module, 5-signal processing module, 6-light source control module, 7-data outputting module.
Embodiment
For making object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is described in further detail.
With reference to shown in Fig. 1, active air chamber structure in the present embodiment and optoacoustic spectroscopy gas sensing system, comprise near infrared DFB semiconductor laser 1, photoacoustic cell 2, microphone 3, photoelectric detection module 4, signal processing module 5, light source control module 6 and data outputting module 7, near infrared DFB semiconductor laser 1 is directly packaged as a whole with one end of photoacoustic cell 2, and to form entirety be that (this structure can make photoacoustic signal only longitudinally propagate for the photo acoustic gas cell of dumbbell shape structure, and have almost no change at radial and angle, thus be conducive to the detection of photoacoustic signal), microphone 3 is arranged on the outside of photoacoustic cell 2, for detecting the intensity of the pressure wave signal formed in photoacoustic cell 2, and be translated into electric signal, the photosurface of photoelectric detection module 4 aim at photoacoustic cell 2 bright dipping end, for light signal is converted into electric signal, the output terminal of photoelectric detection module 4 and microphone 3 is all connected to the input end of signal processing module 5, and an output terminal of signal processing module 5 is connected with light source control module 6, another output terminal is connected with data outputting module 7, light source control module 6 is connected with the control end of near infrared DFB semiconductor laser 1.
Photo acoustic gas cell is single port or two-port air chamber (without emergent light monitoring under single port, having emergent light to monitor under dual-port).
Signal processing module 5 comprises lock-in amplifier, and signal processing module 5 utilizes phase locking technique to realize weak signal by lock-in amplifier and extracts.
The present invention one end that the is near infrared DFB semiconductor laser 1 of improvement is direct and photoacoustic cell 2 is packaged as a whole, and makes photoacoustic cell 2 and near infrared DFB semiconductor laser 1 become an active photo acoustic gas cell structure; Light source control module 6 is connected with near infrared DFB semiconductor laser 1 control end, utilizes the generation of semiconductor laser frequency modulation technology have the exciting light of acoustics modulation signature and be directly injected in photoacoustic cell 2; Be stimulated after specific gas molecule absorption luminous energy in photoacoustic cell 2, transit to the high-energy state of vibrational energy level, and then be kinetic energy by radiationless transition by Conversion of Energy, thus in photoacoustic cell 2 mineralization pressure ripple; Utilize microphone 3 to detect the intensity of the pressure wave signal formed in photoacoustic cell 2, and be translated into electric signal; Light signal is changed into electric signal by photoelectric detection module 4; Signal processing module 5 receives the electric signal of microphone 3 output terminal and the electric signal of photoelectric detection module 4 output terminal, and carries out filter amplifying processing to the electric signal received; An output terminal of signal processing module 5 is connected with light source control module 6, utilizes output signal to carry out negative feedback to light source control module 6, thus guarantees near infrared DFB semiconductor laser 1 stable output; Another output terminal of signal processing module 5 by interface circuit by Signal transmissions to data outputting module 7, carry out data processing and display.According to the relation of sound pressure signal amplitude and incident intensity, gas molecules sorb coefficient and content, thus the content of gas of determining to be stimulated in photo acoustic gas cell, finally obtain gas concentration to be measured.
Gas molecule obeys Lambert-Beer (Lambert-Beer) law to the absorption of light intensity.Optoacoustic spectroscopy is the calorimetric spectral technique of a kind of high sensitivity based on optoacoustic effect, great dynamic range.The essence of photoacoustic signal is the energy conversion of light, heat, sound, electricity.
In photo acoustic gas cell (photoacoustic cell), gas is in the molecule of excited state because of radiationless relaxation generation heat H (r, t) be the function of position and time, incident intensity is made to be I (r, t), H (r, t)=α I (r, t), wherein α is gas molecules sorb coefficient, when incident wavelength is certain, gas concentration to be measured (heat produced by gas absorption process is to characterize gas concentration to be measured) can be determined by the power of H (r, t).
Acoustic pressure P (r, t) in order to describe acoustic disturbance in gas to be measured, P (r, t)=P-P
0, P is general pressure, P
0for pressure mean values, tested gas absorption light modulated forms heat H (r, t), can regard the energy source of Gas Vibration as, the sound field in photo acoustic gas cell
it is the superposition of multiple acoustic pressure distribution.And normal mode solution P
jbe decided by the shape of photo acoustic gas cell.
In photo acoustic gas cell actual design, it is usually made to be operated in normal mode P
jr () amplifies (ω=ω with the resonance obtaining sound pressure signal
j).At the r place of photoacoustic cell 2, the sound pressure signal in photoacoustic cell 2 is:
In formula, γ is the specific heat ratio of gas, Q
jfor quality factor, the accumulation of acoustic energy in air chamber and lost speed are reacted, ω
jthe resonant frequency of photoacoustic signal, L
cthe length of air chamber, V
cthe capacity of air chamber, I
jit is incident intensity.
Sound pressure signal P (r, ω is detected by microphone 3
j), and the injecting electronic signal of correspondence is carried out related operation to the lock-in amplifier of signal processing module 5, effectively suppress uncorrelated noise thus improve signal to noise ratio (S/N ratio), also can extract phase place and the frequency of photoacoustic signal simultaneously easily.
Obviously, above-described embodiment is only for example of the present invention is clearly described, and is not the restriction to embodiments of the present invention.For those of ordinary skill in the field, be still among protection scope of the present invention according to spirit institute's apparent change of extending out of the present invention or change.
Claims (4)
1. an active air chamber structure and optoacoustic spectroscopy gas sensing system, it is characterized in that: it comprises integrated optical source, photoacoustic cell, microphone, photoelectric detection module, signal processing module, light source control module and data outputting module, described integrated optical source one end that is direct and photoacoustic cell is packaged as a whole and forms active photo acoustic gas cell, described microphone is arranged on the sidewall of photoacoustic cell, for detecting the intensity of the sound pressure signal formed in photoacoustic cell, and is translated into electric signal; What the photosurface of described photoelectric detection module aimed at photoacoustic cell goes out optical port, for light signal is converted into electric signal; The output terminal of photoelectric detection module and microphone is all connected to the input end of signal processing module, and an output terminal of signal processing module is connected with light source control module, another output terminal is connected with data outputting module; Described light source control module is connected with the control end of integrated optical source.
2. active air chamber structure according to claim 1 and optoacoustic spectroscopy gas sensing system, is characterized in that: described integrated optical source adopts near infrared DFB semiconductor laser.
3. active air chamber structure according to claim 1 and optoacoustic spectroscopy gas sensing system, is characterized in that: described active photo acoustic gas cell is single port or two-port air chamber.
4. active air chamber structure according to claim 1 and optoacoustic spectroscopy gas sensing system, is characterized in that: described signal processing module comprises lock-in amplifier, and signal processing module utilizes phase locking technique to realize weak signal by lock-in amplifier and extracts.
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| CN106769973A (en) * | 2017-03-03 | 2017-05-31 | 江苏舒茨测控设备股份有限公司 | Ammonia gas detection means and method are detected using photocaustic spectroscopy |
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| CN107884344A (en) * | 2017-11-03 | 2018-04-06 | 江苏国电南自海吉科技有限公司 | A kind of optoacoustic spectroscopy gas sensing system of the active air chamber based on semiconductor laser |
| CN109374529A (en) * | 2018-09-13 | 2019-02-22 | 大连理工大学 | A kind of resonant photoacoustic cell of partly beginning to speak |
| CN109490216A (en) * | 2019-01-07 | 2019-03-19 | 大连理工大学 | A kind of the Laser Photoacoustic Spectroscopy trace gas detection instrument and method of calibration-free |
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Cited By (10)
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| CN107884344A (en) * | 2017-11-03 | 2018-04-06 | 江苏国电南自海吉科技有限公司 | A kind of optoacoustic spectroscopy gas sensing system of the active air chamber based on semiconductor laser |
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| CN109490216A (en) * | 2019-01-07 | 2019-03-19 | 大连理工大学 | A kind of the Laser Photoacoustic Spectroscopy trace gas detection instrument and method of calibration-free |
| CN109490216B (en) * | 2019-01-07 | 2021-02-19 | 大连理工大学 | Calibration-free laser photoacoustic spectrum trace gas detection instrument and method |
| CN110333190A (en) * | 2019-07-05 | 2019-10-15 | 大连理工大学 | A kind of diffusion type optoacoustic microcavity gas sensor |
| CN113281261A (en) * | 2021-03-26 | 2021-08-20 | 安徽波汇智能科技有限公司 | Novel photoacoustic spectrum gas sensor |
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Application publication date: 20160406 |