CN106483069A - Trace gas on-line analyses device based on cavity attenuation and vibration technique - Google Patents
Trace gas on-line analyses device based on cavity attenuation and vibration technique Download PDFInfo
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Abstract
The present invention relates to trace Fe field, more particularly, to the trace gas on-line analyses device based on cavity attenuation and vibration technique.Laser instrument exports a branch of laser through wavelength modulation, it is coupled into optical resonator, optical resonator is the straight chamber equipped with high reflection concave mirror for the two ends, and chamber has air inlet and gas outlet, laser produces resonance in intracavity after multiple reflections, and exports stable laser beam to laser detector；Optoisolator is between laser instrument and optical resonator, prevents laser-bounce from returning laser instrument；After laser detector detects laser output power and exceedes certain threshold value, laser instrument is turned off by current-modulation by signal processing and control module, after detection turns off laser instrument, the time interval of optical resonator output laser attenuation to the bottom threshold setting carrys out the concentration of reverse intracavity gas；Temperature control module is responsible for controlling optical resonator in specific temperature, and chamber length is adjusted.
Description
Technical field
The present invention relates to trace Fe field, more particularly, to the trace gas on-line analyses device based on cavity attenuation and vibration technique.
Background technology
Cavity attenuation and vibration technique is as a kind of feasible trace gas on-line monitoring, it is high-resolution, the high accuracy absorption spectroscopy techniques being grown up based on passive cavity intracavity absorption spectrum, it mainly obtains the absorptance of intracavity medium by measuring ring-down time in high reflection chamber for the light.Cavity attenuation and vibration technique and intracavity absorb, the difference of long-range absorption spectroscopy techniques be its be not concerned with light intracavity reflecting number of times number, and pay close attention to the ring-down time in intracavity for the light, it is the ratio of an intensity, the fluctuation amplitude avoiding laser intensity is to the impact measuring, thus the precision of measurement greatly improves.
Declining and swinging chamber two ends is two sides high reflection eyeglass.When a laser pulse, to be injected into chamber a length of
In said process, injection declines, and swing chamber is the very short pulse laser of coherence length, does not interfere effect during resonator round-trip.But in the experiment of pulse cavity ring-down spectroscopy, because pulse laser live width is typically wider, resonator cavity multimode oscillation therefore can be caused, and the beat frequency between due to each pattern, many e indexes effect (being confirmed) of deamplification can be led to by experiment, final reduction detection sensitivity, in order to improve detectivity, had developed continuous wave cavity ring-down technology later.
After continuous wave laser, not only the live width of such laser instrument is relatively very narrow（<2MHz）And near infrared band can also using compact, price is low, low-power consumption and the semiconductor laser diode that need not freeze are as light source, the volume of measuring system and cost can be reduced further so that this system becomes a reality in the popularization of the application such as portable light spectrometry and long-range Trace gas detection.After using continuous wave laser source, due to injection resonator cavity is a branch of continuous laser, therefore complicated interference effect will be formed in intracavity, how efficient coupling entrance optical resonator is related to pattern theory, including contents such as condition of resonance, longitudinal mode, transverse mode, pattern match to laser.
（
1
）, condition of resonance
Situation for uniform plane wave roundtrip propagation in plane-parallel resonator, when light wave reflects in hysteroscope, incidence wave and echo can interfere, repeatedly toward multiple-beam interference will occur during interflection, in order to be able to form stable oscillation stationary vibration it is desirable to wave energy is strengthened because of interfering in intracavity.Known by interference theory, the condition of generation constructive interference is：Ripple from certain point, when returning original position within one week through intracavity round trip, should with initial ripple with
In, the e index decay in time of its light intensity, because intracavity has the absorptance that the under test gas having absorption to laser can be finally inversed by gas by the ring-down time τ of Laser Measurement, thus obtain the concentration value of under test gas.
In said process, injection declines, and swing chamber is the very short pulse laser of coherence length, does not interfere effect during resonator round-trip.But in the experiment of pulse cavity ring-down spectroscopy, because pulse laser live width is typically wider, resonator cavity multimode oscillation therefore can be caused, and the beat frequency between due to each pattern, many e indexes effect (being confirmed) of deamplification can be led to by experiment, final reduction detection sensitivity, in order to improve detectivity, had developed continuous wave cavity ring-down technology later.
After continuous wave laser, not only the live width of such laser instrument is relatively very narrow（<2MHz）And near infrared band can also using compact, price is low, low-power consumption and the semiconductor laser diode that need not freeze are as light source, the volume of measuring system and cost can be reduced further so that this system becomes a reality in the popularization of the application such as portable light spectrometry and long-range Trace gas detection.After using continuous wave laser source, due to injection resonator cavity is a branch of continuous laser, therefore complicated interference effect will be formed in intracavity, how efficient coupling entrance optical resonator is related to pattern theory, including contents such as condition of resonance, longitudinal mode, transverse mode, pattern match to laser.
In plane-parallel resonator, frequency meets formula（5）Plane stationary field be referred to as chamber eigen mode, be characterized in：Transversal in-plane field distribution in chamber is uniform, and the axis direction along chamber（Longitudinally）Form standing wave, the node number of standing wave is determined by value q, and the intracavity axial fjeld distribution being characterized by integer q is generally referred to as the longitudinal mode in chamber, q claims longitudinal mode ordinal number, different q values corresponds to different longitudinal modes, the different frequency of correspondence, is commonly referred to Free Spectral Range between two resonant frequencies.
（
3
）, transverse mode
Longitudinal mode is the longitudinal stability field distribution that light wave is formed in the multiple round-trip transmission of intracavity, and the formation of transverse mode is also relevant in intracavity multiple round-trip transmission process with light wave.Because cavity mirror physical dimension is limited, loss will necessarily be produced because of the diffraction effect at mirror edge when light wave round-trip transmission between two mirrors, when determining the formation of the horizontal field distribution of endovenous laser vibrational stabilization, diffraction will play a major role.It can thus be seen that longitudinal mode is general only relevant with the chamber length of the wavelength resonant cavity of incident illumination, and transverse mode is relevant with the diffraction effect of hysteroscope during light wave transmissions, and the wavelength of incident illumination affects very little to it.
（
4
）, pattern match
Pattern match refers to that incoming laser beam enters in optics cavity, and its with a tight waist and radius of curvature is equal with the with a tight waist of optics cavity basic mode TEMmn and radius of curvature.In the case of pattern match, incident single mode Gaussian beams the corresponding single mode of activating system one, only frequency and chamber pattern can only occur the light of resonance just can be coupled into decline and swing chamber, and such light intensity can be gathered in chamber, reaches largest loop power.
For continuous wave laser pattern match exist Mode Coupling mate with frequency of both problem.When the energy of laser can not proceed to corresponding passive cavity system mould（I.e. mode mismatch）, emergence pattern is changed, has excited multistage transverse mode in passive intracavity.The reason cause mode mismatch has a lot, they can be attributed to two classes：Hysteroscope mismatch（Beam radius mismatch and wave-front curvature mismatch etc.）And cavity mirror misalignment（The translation of incident light axis and passive cavity light between centers and inclination etc.）.
In addition to Mode Coupling, laser also needs to reach frequency with optical resonator and mates, that is, meets condition of resonance in frequency.Due to reasons such as processing technique, such as take no action to, both frequency couplings difficult to realize, this will make cavity-type BPM method measurement cannot be carried out.
Tuning laser mid frequency or adjust the position that passive cavity chamber length to change chamber longitudinal mode with this, is to realize the usual way that narrow spectral line laser is mated with passive cavity frequency at present.
Content of the invention
The purpose of invention：In order to provide a kind of trace gas on-line analyses device preferably based on cavity attenuation and vibration technique for effect, specific purposes are shown in the multiple substantial technological effects being embodied as part.
In order to reach as above purpose, the present invention adopts the following technical scheme that：
It is characterised in that device includes laser instrument, laser instrument connects optoisolator to trace gas on-line analyses device based on cavity attenuation and vibration technique；Optical isolator side is optical resonator, and optical resonator comprises temperature control module, also comprises the laser detector positioned at optical resonator side, and above each part connects signal processing and control module；Laser instrument exports a branch of laser through wavelength modulation, it is coupled into optical resonator, optical resonator is the straight chamber equipped with high reflection concave mirror for the two ends, and chamber has air inlet and gas outlet, laser produces resonance in intracavity after multiple reflections, and exports stable laser beam to laser detector；Optoisolator is between laser instrument and optical resonator, prevents laser-bounce from returning laser instrument；After laser detector detects laser output power and exceedes certain threshold value, laser instrument is turned off by current-modulation by signal processing and control module, after detection turns off laser instrument, the time interval of optical resonator output laser attenuation to the bottom threshold setting carrys out the concentration of reverse intracavity gas；Temperature control module is responsible for controlling optical resonator in specific temperature, and chamber length is adjusted.
The further technical scheme of the present invention is, described thermal module effect is as follows, effect of expanding with heat and contract with cold first with resonator cavity, first with temperature, effective cavity length is adjusted, reach the purpose of longitudinal mode preliminary matches, then utilize temperature control technology by the temperature control of resonator cavity in target particular value, finally reach the matched of lasing light emitter and resonator cavity again with laser wavelength modulation technology.
Using the present invention of as above technical scheme, have the advantages that with respect to prior art：It is different from the gas analyzing apparatus of general cavity attenuation and vibration technique, this device is adjusted and to be carried out the pattern match of laser instrument and resonator cavity by integrated application laser wavelength modulation, optical resonator destructing design and temperature control cavity length, eliminate the long modulating part in chamber of acoustooptic switch and PZT, simplify structure, improve system reliability.
Brief description
Fig. 1 designs basic framework for whole equipment；
Fig. 2 is Laser Drive design overall block diagram；
Fig. 3 is constant-current circuit schematic diagram；
Fig. 4 is peak signal detection process；
Fig. 5 is PID equation；
Fig. 6 is PID control schematic diagram；
Fig. 7 swings curve for original declining；
Fig. 8 is data fitting result after logarithmic transformation；
Fig. 9 is the light intensity transmissison characteristic under different reflectivity.
Specific embodiment
With reference to Fig. 1-Fig. 9, embodiments of the invention are illustrated, embodiment is not construed as limiting the invention：
Semiconductor laser has the advantages that small volume, monochromaticity are good, energy consumption is low, long working life, has obtained increasingly extensive application in fields such as scientific research, military affairs, industry.Semiconductor laser is injected as energisation mode using electric current, and its operating characteristic and service life depend greatly on the quality of driving power supply performance used.Meanwhile, the output of laser instrument is directly related to injection current and die temperature.Therefore, for obtaining high-quality output beam, realize the wavelength modulation to laser instrument, need noise spectra of semiconductor lasers to realize strict electric current and temperature control.In addition; the PN junction of semiconductor laser diode is more fragile; slightly voltge surge; it is possible to affect Output optical power or the beam quality of laser diode; even cause permanent destruction; therefore in addition to the tube core of noise spectra of semiconductor lasers realizes strict temperature control and flow control, also it to be taken with some necessary protective measures, it is to avoid maloperation or unexpected factor cause to it to damage.
Chamber Research on Technology of Schema Matching
According to the feature of pattern theory and optical resonator, carrying out, it is necessary to consider the pattern match of light source and optical cavity when cavity attenuation and vibration technique is realized, mating with longitudinal mode including transverse mode coupling, that is, Mode Coupling is mated with frequency.When the pattern of LASER Light Source and optical resonator mismatches, light cannot be coupled in optical cavity, and such outgoing optical signal can be extremely weak, will have a strong impact on the measurement of ring-down time.Therefore the matching principle of chamber pattern must be furtherd investigate, be that the realization of trace gas analysis based on cavity attenuation and vibration technique is taken a firm foundation.
Mainly adopt collimating mirror to reduce laser light incident hot spot for transverse mode coupling, and using methods such as cross imagings, two pieces of high reflection eyeglasses are tuned into parallel and vertical with incident axle.For longitudinal mode coupling, currently the main method solution using installation PZT piezoelectric ceramics on a face high reflection mirror, using the periodic vibration of piezoelectric ceramics, makes chamber length produce cyclically-varying, chamber progress line period is scanned to reach the purpose of longitudinal mode coupling.
The creative proposition of this project is first with the effect of expanding with heat and contract with cold of resonator cavity, first with temperature, effective cavity length is adjusted, reach the purpose of longitudinal mode preliminary matches, then utilize high precision temperature control technology by the temperature control of resonator cavity in particular value, finally reach the matched of lasing light emitter and resonator cavity again with laser wavelength modulation technology.
The semiconductor laser of high stability drives and protection is the basis that system normally, effectively operates.The actuation techniques of semiconductor laser generally adopt constant current drive mode, under this working method, by negative-feedback principle control loop, directly provide the effective control of driving current.Additionally, the curtage spike of transient state, and excessively stream, overvoltage all can damage semiconductor laser, it is also contemplated that special anti-surge measure and protection circuit therefore in drive circuit.
The semiconductor laser of this Project design drives modulation circuit to be made up of five major parts, including constant-current circuit, soft start, current-limiting protection, modulated signal producing circuit, temperature-control circuit.Constant-current circuit produces high stability driving current.The effect of soft start is to eliminate surge that may be present in circuit, prevents the harm to laser instrument for the surge.For avoiding causing the expendable damage of semiconductor laser due to factors such as excessively streams, then add current-limiting protection in the driving circuit.Modulated signal producing circuit realizes modulation and frequency-adjustable.Temperature control is mainly realized the accurate of laser temperature and is controlled it is ensured that the stability of laser works.As shown in Figure 2.
Constant-current circuit to realize constant current using negative voltage feedback adjustment circuit, and the operation principle of circuit is shown in Fig. 3.Produce the voltage reference of a high precision high stability first by reference circuit, when input voltage increases or load change so that output current is changed, sample circuit will obtain a certain proportion of output voltage error information, then after it being compared with voltage reference, error amplifying circuit is applied to adjustment circuit adjustment output current the error signal being exaggerated, thus forming the closed loop system of a profound and negative feedbck, realizing the regulation to output, reaching the purpose of stabling current.
Current modulated passes through the DDS functional realiey of FPGA, is produced using the signal that a piece of FPGA chip can complete signal source and its controls.As long as change the ROM data in wave memorizer it is possible to produce random waveform simultaneously.This programme with FPGA as core, using a high accuracy 16 digit weighted-voltage D/A converter（DAC）, by changing the ROM data storage in DDS system, low frequency triangular modulation signal can be produced.
Temperature control mainly adopts WTC3243 module to realize, this module is the laser diode temperature controller of a superhigh precision, using PI closed loop control, can easily be integrated in the pcb board of design, the input current of refrigerator in semiconductor laser can be controlled, to reach the purpose of accurate temperature control.
This project is passed through the methods such as integrated application laser wavelength modulation, optical resonator destructing design and the regulation of temperature control cavity length and is cleverly solved frequency mode matching problem, instead of the acoustooptic switch of costliness and the complicated long modulated structure in PZT chamber.
LASER Light Source and optics decline and swing the pattern matching problem in chamber
Theoretical according to multiple-beam interference, in intracavity multiple reflections, the wavelength of such as fruit caving length and laser can not mate laser, it will because interfere leading to endovenous laser energy attenuating, that is, the laser of laser instrument is unable to efficient coupling and enters optical resonator.Therefore laser source wavelength and the pattern matching problem of optical resonator must solve.Common practice is to install PZT crystal oscillator pottery in one piece of high reflection eyeglass, vibrates to enter an actor's rendering of an operatic tune long scan according to certain frequency by exciting PZT, thus reaching the purpose of optical maser wavelength and cavity length matching.Installing PZT on high reflective mirror needs to ensure incidence and the outgoing that PZT does not stop laser, PZT also to be ensured therefore will not adjust chamber to considerably increase the installation of optical resonator using PZT and adjust chamber difficulty because of making lens tilt etc. lead to the transverse mode of optical resonator to be lacked of proper care in vibration simultaneously.
During due to single employing laser wavelength modulation method, the wavelength modulation range of semiconductor laser is limited, typically in more than ten nm, and be used for gasmetry laser instrument and be generally near infrared band, wavelength is in more than 700nm, if the longitudinal mode resonance point distance of therefore effective cavity length and coupling differs hundreds of nm, will be unable to complete frequency mode coupling by wavelength modulation.The installation of optical resonator cannot make effective cavity length error control between tens nm, therefore single is unable to reach purpose using laser wavelength modulation method.
Using common quartz glass as cavity material（Can also have the material of suitable coefficient of thermal expansion and contraction using other as cavity material）, when chamber length is more than 30cm, if temperature change is more than 20 degrees Celsius, change of cavity length will exceed 2000nm.When single using laser wavelength modulation method be unable to reach frequency mode coupling when, chamber is changed by the temperature setting that temperature control modules constantly change cavity long, till can reach frequency mode coupling using laser wavelength modulation method, temperature now is set as cavity temperature, cavity temperature general control is at 40 to 60 degrees Celsius.The frequency mode matching problem of LASER Light Source and optical resonator not only can be solved by temperature control, the impact to intracavity gas absorbance for the ambient temperature change can also be avoided.
The trace on-line gas analysis equipment based on cavity attenuation and vibration technique that this Project design is realized is after entering row mode preliminary matches in addition it is also necessary to carry out high accuracy frequency coupling using laser wavelength scan.When carrying out laser wavelength scan, the signal that laser detector detects changes with matching degree, and matching degree is higher, and signal output is bigger.Find that the current analytical equipment based on cavity attenuation and vibration technique simply simply sets a threshold value in detailed investigation of related literatures, when signal is detected and exceeding a certain threshold value, turn off lasing light emitter.But intracavity gas are related to gas concentration to the absorption intensity of laser, particularly in trace gas analysis, the ppb level change of gas concentration also can produce impact to measurement, and the concentration change of ppb level can occur within the time of delicate level, therefore simply set a threshold value and may not reach preferable detection state.Cleaning Principle therefore according to cavity attenuation and vibration technique, needs quick detection to go out this peak signal, to carry out quick laser cutting.
Different from general peak signal detection technique, the peak signal detection in this project not only needs the speed being exceedingly fast in addition it is also necessary to the noise peak signal that power supply disturbance, outside electromagnetic interference etc. cause can be eliminated.Therefore, not only devise peak signal detection method in this project it is also proposed that interference protection measure.
Under peak detection mode, ADC is sampled with sample rate as high as possible, so can catch narrower burr signal.In this project, the sample rate of ADC under peak detection mode is set to 800 M, the speed being equivalent to peakvalue's checking is 800MS/s.Due to the data speed after ADC conversion quickly, FPGA is difficult to process, and therefore first with the differential receivers within FPGA, these data is done serioparallel exchange so that data bit is changed into 64, is equivalent to the data of 88, thus speed is lowered.When the sample rate of ADC is 800M, after reduction of speed, clock speed is changed into 100 MS/s.Then select maximum and minima from 88 data, compare with the maximum of last time and minima respectively, maximum than last time is big just to be remained, and otherwise keeps constant；Minima than last time is little just to be remained, and otherwise also keeps constant.After number of comparisons reaches the value of setting, final maximum and minima output.The number of comparisons setting can be used for controlling the peak signal pulsewidth of detection.Processing speed after FPGA processes ADC conversion is substantially increased by this method, signal detection process is as shown in Figure 4.
In addition, because laser wavelength scan is by a fixed cycle signal modulation, the peak signal of the detection peak value that only one of which needs in each cycle, and signal width is basically identical, according to this feature, may determine that whether the signal detecting is the peak signal needing, thus avoiding interference the impact at peak.
Resonator cavity high precision temperature control problem
The temperature control of resonator cavity is to ensure that the key of longitudinal mode coupling, also one of key of whole system normal work.Because the volume of optical resonator is larger, general in length in 30cm, it is not suitable for being heated with heating plate, the heater strip that therefore have selected diameter 0.4mm in project is heated, outside optical resonator, it is wound around heater strip, outside is encapsulated with insulation material again, and enclosed inside critesistor, for thermometric.
PID control method is a kind of classical industrial control method, is used for optical resonator is realized accurate temperature control here, and ultimate principle is as shown in Figure 6：PID control is to error signal（e(r)=r(t)-e(t)）Carry out ratio, integrate, differentiate, by proportion differential (PD) control system, overshoot can be reduced, but not eliminate steady-state error, and increase an integral term and just can eliminate steady-state error.PID equation is Fig. 5 institute
In order to avoid electromagnetic interference, it is provided without conventional pulse duration modulation method in project and controls heating, but using constant current heating, control temperature change by the minor variations of control electric current.Therefore here size of current as controlled quentity controlled variable, as controlled device, as control targe, the temperature detecting is as feedback quantity for the temperature value of setting for temperature.By three parameter values in continuous adjustment pid algorithm, so that system is reached stable, and achieve 0.1 degree of accuracy of temperature control.
Decline and swing signal optimization extraction problem
Declining and swinging signal optimization extraction problem is one of cavity attenuation and vibration technique research major issue.Because flooding a little to obtaining different signals in the detection of variable concentrations gas, and in the continuous on-line monitoring of gas, tested gas concentration being inevitably continually changing, therefore signal floods and is a little also being continually changing.In data matching, how to choose effective optical signal and be intended to one of problem of solution with noise signal separation.
For the hydrogen sulfide analysis system set up in project, system is placed under high-purity nitrogen environment, carries out test experiments, detection obtains 32 groups of data, carries out logarithmic transformation, then carry out data matching after being averaging.In conjunction with Fig. 7 and Fig. 8；
Because experiment is carried out under high-purity nitrogen environment, can see that the data that signal floods near a little will adversely affect to result from figure.During the continuous on-line monitoring of trace gas, multi-group data cannot be obtained, the data that signal floods near a little will produce considerable influence to testing result, may produce larger error, therefore will guarantee enough surpluses in the selection course with noise signal separation for effective optical signal.We choose the effective optical signal of offline conduct and noise signal separation in the project.According to experimental result, we choose 15% of signal intensity during laser cut-out as effective optical signal and noise signal separation.
Plano-concave high reflection mirror in optical resonator is the critical component of optical resonator, and its technical parameter determines the detection performance of whole equipment, and particularly its high reflection performance is the important guarantee of cavity-type BPM gas analyses.But, the albedo parameters of high reflection mirror are also the deciding factor of its price, swing the impact of result by studying cavity mirrors reflectivity and signal being declined, there is provided for high reflection mirror type selecting in project and instruct, to reach acquirement optimal balance between equipment cost and instrument performance, it is that the industrialization of project lays the foundation.
Light enters into decline and swings in chamber, meeting roundtrip between two hysteroscopes, transmissive portion light intensity simultaneously, and when entrance reflecting mirror passes through resonant condition, the transmissison characteristic with the different cavity of cavity mirrors reflectivity can change.Fig. 9 is the light intensity transmission characteristic representing under different cavity mirrors reflectivities obtaining on project experiment porch.When incident illumination and chamber mode resonances, laser is injected into decline and swings in chamber, is located at t=0 moment intracavity light intensity and reaches maximum, be then cut off laser, intracavity light intensity starts gradually to decay.It can be seen that with the increase of cavity mirrors reflectivity, the intensity of the accumulation of intracavity light intensity and decay is gradually reduced.This is because cavity mirrors reflectivity is bigger, the fineness in chamber is higher, and chamber loft width is narrower, rises and ring-down time all reduces therewith.
In addition, Fig. 9 also show the many amplitude oscillatory process under certain hysteroscope speed and reflectance.Although because light is in the every round trip of intracavity, because hysteroscope transmission effect photon numbers can reduce, in the case that light source is not cut-off, photon still can continue that being injected into declines swings in chamber.If being lost constant in holding chamber, increase cavity mirrors reflectivity, then absorbance can accordingly reduce.This can increase the number of photons of intracavity, and the therefore intensity of constructive and destructive interference all can strengthen.This characteristic is reflected by strengthening with the increase oscillation amplitude of R.With the effect of destructive interference, photon leaves to decline and swings chamber, and photon numbers can gradually decrease.
According to considering of experimental result and cost, the reflectance determining high reflection mirror in project need to be more than 99.9%, and this can ensure certain cost advantage it is also ensured that suitable detection performance.
As preferred：When carrying out Laser Modulation driving design, laser frequency scanning speed can not be too high.Meanwhile, when rate of scanning is less than 100Hz/s, the increase of intracavity relative light intensity is inconspicuous, and ring-down time change is also inconspicuous.Therefore consider, as laser frequency scanning speed, this speed ensure that intracavity light intensity to project alternativess 100Hz/s, also ensure that detection speed simultaneously.
As a comparison：Method in this project：
（1）Optical resonance intracavity is not reequiped, install simple
（2）Impact will not be produced on high reflection mirror in use, transverse mode will not be caused to change, reliability is high
（3）The impact of ambient temperature can be avoided by temperature control.
Traditional method：
（1）On a piece of high reflection mirror, PZT piezoelectric ceramics to be installed, and incident light beam strikes can not be affected, during vibration it must also be ensured that eyeglass longitudinally perpendicular, installation difficulty is big, and reliability is low；
（2）Ambient temperature change can produce impact to optical cavity resonance.
Currently, common Atmospheric Trace dusty gass detection meanss have open light path trace gas analysis based on difference, the analytical equipment based on long light path gas absorption cell, spectrophotometric spectra quasi-instrument etc., all there is this or that problem in these instruments, be unfavorable for widely using in atmosphere environment supervision.For example, the trace gas analysis device based on open light path, due to achieving the GAS ABSORPTION light path of upper km, can reach very low Monitoring lower-cut, the realization of long open path leads to installation maintenance requirement high Just because of this, and is difficult to portable, therefore promotes the use of difficulty on a large scale very big.Analytical equipment based on long light path gas absorption cell is easy to use, but this quasi-instrument is based on direct absorption spectroscopy techniques, and effective absorption light path that gas absorption cell enables is still limited, generally tens meters, the Monitoring lower-cut that therefore can reach is still higher to monitor it is impossible to meet part trace species analysis.The main advantage of spectrophotometric spectra quasi-instrument is can to analyze many kinds of substance simultaneously, but is also easy to produce interference between each component gas, generally requires and carries out pretreatment to exclude material interference, is not suitable as atmospheric trace gas on-line analyses device and is promoted.
It is widely used based on the trace gas in-line analyzer of cavity attenuation and vibration technique, one of main application is to carry out on-line monitoring to the trace contamination gas in air, such as H2S, nitrogen oxides etc..Because cavity attenuation and vibration technique is that laser forms after stable resonant oscillation in optical resonance intracavity through multiple reflections, turn off laser instrument, measurement optical resonator exports the time interval that laser energy decays to preset lower limit, the essence of this process is still laser absorption spectroscopy, but eliminate LASER Light Source and export the interference that energy variation is brought, intracavity absorbs light path up to several kms simultaneously, or even tens kms, can reach extremely low test limit.Can complete extremely low concentration dusty gass in air on-line monitoring analysis, simultaneously this instrument have small volume, low in energy consumption, carry the advantages such as easy to use, calibration-free, can be very good to substitute current Atmospheric Trace dusty gass analytical equipment.
In sum, cavity attenuation and vibration technique is incorporated into trace contamination gas detecting in air and can overcome the shortcomings of current concentration techniques means, specifically see table shown.
Atmospheric trace gas monitoring meanss compare
Technological innovation
1
, determine laser cut-out point by using detection signal peak value detection method, improve the reliability of system detectio
The trace on-line gas analysis equipment based on cavity attenuation and vibration technique that Project design is realized is after entering row mode preliminary matches in addition it is also necessary to carry out high accuracy frequency coupling using laser wavelength scan.When carrying out laser wavelength scan, the signal that laser detector detects changes with matching degree, and matching degree is higher, and signal output is bigger.
The general point instrument equipment based on continuous-wave cavity ring-down technology, when entering the modulation of an actor's rendering of an operatic tune length, turns off LASER Light Source when detecting after optical resonator output laser energy reaches certain threshold value.Being set in of threshold value determines during instrument testing, is determined according to the ceiling capacity of laser output in resonator cavity in the long modulated process in chamber, generally according to the ratio-dependent of ceiling capacity.The method is simply effective when carrying out cavity lens loss measurement using cavity attenuation and vibration technique, but there is larger problem when carrying out trace gas on-line analyses.Because intracavity gas are related to gas concentration to the absorption intensity of laser, particularly in trace gas analysis, the ppb level change of gas concentration also can produce impact to measurement, and the concentration change of ppb level can occur within the time of delicate level, therefore simply set a threshold value and may not reach preferable detection state.Higher in gas concentration, when absorbing more abundant, the threshold value of setting may not reached it is impossible to carry out the analysis of higher concentration gas；And when gas concentration is very low, it is likely to result in too early shutoff LASER Light Source, lead to resonance insufficient, affect Detection results.
Cleaning Principle therefore according to cavity attenuation and vibration technique, quick detection goes out this peak signal, carries out quick laser cutting, to improve Detection results after peak signal is detected.Due to employing relatively low wavelength modulating speed, therefore carry out laser cut-out again through the time of ns level after peak value appearance and do not interfere with measurement result.The detection range of instrument can effectively be expanded using the method.
In project, two methods are contrasted.Generally, the setting of laser cut-out threshold value, firstly the need of recording the maximum cavity output energy that pattern match is in extremely low tested gas concentration atmosphere, generally according to the 80% to 90% of this value ratio given threshold, takes 85% given threshold in the contrast of project.In experiment, the H2S sample gas of 5 groups of variable concentrations is detected.Standard specimen is the trace gas that project team adopts dilution method configuration, and concentration is about 10ppb, 100ppb, 400ppb, 800ppb, 2ppm.
Detect that five kinds of sample gas respectively obtain signal ring-down time unit with two methods
us
：
From data in table, effectively increased the detection range of instrument using the method in this project, it is possible to obtain bigger detection range.In table data present non-linear, main cause be sample gas configuration process relatively simple it is impossible to precise control sample gas concentration, but this experiment can fully in this project method effectiveness.
, swing signal fitting error analyses according to declining, intercepted optimal detection data and calculated, improve accuracy of detection
Ring-down time is theoretically that single e arranges number form formula, but this opinion model of simply now thinking.In fact, presence due to factors such as LASER Light Source characteristic, the stability in chamber, the pattern match of interference effect, laser and optical cavity, although taking the distortion that many kinds of measures to avoid signal in system design, the output signal that detector detects still can deviate single e index decay to a certain extent.Therefore data matching is carried out for the signal demand detecting, to obtain ring-down time.Different signals can be obtained flood a little in the detection to variable concentrations gas, and in the continuous on-line monitoring of gas, tested gas concentration is inevitably continually changing, therefore signal floods and is a little also being continually changing.Attention is not had to flood the impact that the data near a little is brought to whole data matching in conventional research.
By experimental studies have found that the data flooded near a little in signal will adversely affect to result.In the cavity lens loss test and gas at rest detection being carried out using cavity attenuation and vibration technique, this impact can be eliminated using the method that collection multi-group data is averaging, but during the continuous on-line monitoring of trace gas, due to multi-group data cannot be obtained to same gas, the data that therefore signal floods near a little will produce considerable influence to testing result, larger error may be produced, therefore will guarantee enough surpluses in the selection course with noise signal separation for effective optical signal.Therefore, give up in this project and detect rear the 10% of data, compare and adopt total data, the method can effectively improve the repeatability of measurement.
Project team has carried out multiple measurement to equally gas, and data is fitted to obtain testing result with two methods, and experimental result is as shown in the table.
The result that the data that two kinds of data cutout methods obtain is fitted（Unit
us
）：
From experimental result, it is fitted comparing using front 90% data the result that obtains is fitted using total data, more preferable measurement reproducibility is had using the result that front 90% data is fitted.
Structure innovation
By using
DFB
Laser instrument
ns
The laser cut-out method of level, has given up the acousto-optic modulator of costliness, has simplified structure, reduces cost
In continuous-wave cavity ring-down technology is realized, after laser output peak signal is detected, need to rapidly switch off incident laser.Traditional continuous-wave cavity ring-down technology all completes the shutoff of incident laser using acousto-optic modulator.Acousto-optic modulator (AOM) is exactly so that the light beam working in Bragg condition is deflected using the method changing frequency of sound wave, is typically gone out incidence system and is constituted by piezoelectric ceramics, transparent medium, laser.When transducer adds high frequency voltage, the vibration of transducer can produce ultrasound wave, in media as well when ultrasound wave passes through solid dielectric, medium molecule electric dipole moment changes, so that the refractive index generating period change of medium, form refractive-index grating, i.e. ultrasonic grating.Light beam will occur diffraction by this grating, thus reaching the effect of light deflection.Currently this acousto-optic modulator generally existing reliability low, expensive the shortcomings of, and system structure complexity and complex circuit designs degree be increased using acousto-optic modulator, reduce reliability.
In this project, from Distributed Feedback Laser as light source, because the output of DFB laser instrument is closely related with its injection current, therefore can realize the switch of laser by current-modulation.At present, require modulation of source speed to reach several GHz in communication field, or even tens of GHz, therefore the ns level of DFB laser instrument turn off relatively easy.This special photoswitch mode, and can be completely eliminated the impact that in conventional system, light shutter device is likely to result in system by the High Speed Modulation of the signal of telecommunication is realized with the speed-sensitive switch of light thus saving electric light or the acoustooptic switch of costliness.
Carry out being compared as follows of instrument design using two methods.
Method in this project：
（1）No acoustooptic switch, low cost, reliability are high
（2）No acoustooptic switch, structure is relatively easy
（3）Laser switch drives and is integrated in Laser Driven, realizes simple.
Traditional method：
（1）Using acoustooptic switch, with high costs, reliability is low
（2）Using acoustooptic switch, structure is relative complex
（3）Acoustooptic switch needs single drive circuit, realizes relative complex
Preferably, after the completion of this patent, touching the mark as follows：
In a creative way, each effect above is individually present moreover it is possible to complete the combination of the above results with a nested structure.
It is clear that the technique effect that above structure is realized is realized, and discounting for additional technical scheme, this patent title can also be a kind of detection method.
It should be noted that multiple schemes that this patent provides comprise the basic scheme of itself, separate, mutually do not restrict, but it can also be mutually combined in the case of not conflicting, reach multiple effects and jointly realize.
Ultimate principle, principal character and the advantages of the present invention of the present invention have been shown and described above.Those skilled in the art is it should be recognized that the present invention is not restricted to the described embodiments; merely illustrating the principles of the invention described in above-described embodiment and description; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements both fall within claimed scope.
Claims (2)
1. it is characterised in that device includes laser instrument, laser instrument connects optoisolator to the trace gas on-line analyses device based on cavity attenuation and vibration technique；Optical isolator side is optical resonator, and optical resonator comprises temperature control module, also comprises the laser detector positioned at optical resonator side, and above each part connects signal processing and control module；Laser instrument exports a branch of laser through wavelength modulation, it is coupled into optical resonator, optical resonator is the straight chamber equipped with high reflection concave mirror for the two ends, and chamber has air inlet and gas outlet, laser produces resonance in intracavity after multiple reflections, and exports stable laser beam to laser detector；Optoisolator is between laser instrument and optical resonator, prevents laser-bounce from returning laser instrument；After laser detector detects laser output power and exceedes certain threshold value, laser instrument is turned off by current-modulation by signal processing and control module, after detection turns off laser instrument, the time interval of optical resonator output laser attenuation to the bottom threshold setting carrys out the concentration of reverse intracavity gas；Temperature control module is responsible for controlling optical resonator in specific temperature, and chamber length is adjusted.
2. the trace gas on-line analyses device based on cavity attenuation and vibration technique as claimed in claim 1, it is characterized in that, described thermal module effect is as follows, effect of expanding with heat and contract with cold first with resonator cavity, first with temperature, effective cavity length is adjusted, reach the purpose of longitudinal mode preliminary matches, then utilized temperature control technology by the temperature control of resonator cavity in target particular value, finally reached the matched of lasing light emitter and resonator cavity again with laser wavelength modulation technology.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101644673A (en) * | 2009-09-09 | 2010-02-10 | 中国科学院光电技术研究所 | Infrared cavity ring-down spectroscopy trace gas detection method based on quantum cascade laser |
| CN103487392A (en) * | 2013-09-30 | 2014-01-01 | 中国科学院西安光学精密机械研究所 | Frequency domain cavity ring-down spectroscopy detection apparatus and method |
| CN103698298A (en) * | 2013-12-29 | 2014-04-02 | 哈尔滨工业大学 | Device for measuring gas concentration based on short cavity enhanced correlation spectroscopy, and method for measuring gas concentration by adopting device |
| CN103760136A (en) * | 2014-01-21 | 2014-04-30 | 河北先河环保科技股份有限公司 | Online monitoring system of greenhouse gas and stable isotope thereof |
| CN203745374U (en) * | 2013-11-12 | 2014-07-30 | 西安泰戈瑞森仪器有限公司 | Cavity ring-down-based online trace gas analysis device |
-
2015
- 2015-08-26 CN CN201510530168.8A patent/CN106483069A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101644673A (en) * | 2009-09-09 | 2010-02-10 | 中国科学院光电技术研究所 | Infrared cavity ring-down spectroscopy trace gas detection method based on quantum cascade laser |
| CN103487392A (en) * | 2013-09-30 | 2014-01-01 | 中国科学院西安光学精密机械研究所 | Frequency domain cavity ring-down spectroscopy detection apparatus and method |
| CN203745374U (en) * | 2013-11-12 | 2014-07-30 | 西安泰戈瑞森仪器有限公司 | Cavity ring-down-based online trace gas analysis device |
| CN103698298A (en) * | 2013-12-29 | 2014-04-02 | 哈尔滨工业大学 | Device for measuring gas concentration based on short cavity enhanced correlation spectroscopy, and method for measuring gas concentration by adopting device |
| CN103760136A (en) * | 2014-01-21 | 2014-04-30 | 河北先河环保科技股份有限公司 | Online monitoring system of greenhouse gas and stable isotope thereof |
Cited By (25)
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