CN203745374U - Cavity ring-down-based online trace gas analysis device - Google Patents
Cavity ring-down-based online trace gas analysis device Download PDFInfo
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- CN203745374U CN203745374U CN201320710426.7U CN201320710426U CN203745374U CN 203745374 U CN203745374 U CN 203745374U CN 201320710426 U CN201320710426 U CN 201320710426U CN 203745374 U CN203745374 U CN 203745374U
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Abstract
The utility model discloses a cavity ring-down-based online trace gas analysis device which consists of a laser, an optical isolator, an optical resonant cavity, a laser detector, a temperature control module and a signal processing and control module, wherein laser light output by the laser enters the optical resonant cavity after passing through the optical isolator; the optical isolator is used for preventing the laser light from being reflected back to the laser; the two ends of the optical resonant cavity are respectively provided with a high-reflection concave mirror; after the laser light is reflected in the cavity for a plurality of times, resonance is generated, and stable laser light is output into the laser detector. When the laser output power is detected to exceed a certain threshold value, the laser is rapidly turned off, and the concentration of gas in the cavity is worked out reversely by detecting the time interval, at which the energy of the laser light output by the optical resonant cavity is decreased to a set lower limit threshold value after the laser is turned off. The temperature control module is used for controlling the temperature of the optical resonant cavity, so that the cavity length can be adjusted. The mode matching between the laser and the resonant cavity can be realized by combining wavelength modulation and cavity length adjustment under temperature control, so that an acousto-optic switch and piezoelectric transducer (PZT) cavity length modulation are replaced, and the system structure is simplified.
Description
Technical field
The present invention relates to mechanical field, relate in particular to a kind of trace gas on-line analysis device that declines and swing based on chamber.
Background technology
Development along with China's industrial sector application, gas analysis instrument has very large market in China, in industrial process analytical applications, there is the analytical instrument demand of sustainable growth, as continuous pollutant monitoring system, at aspects such as productive life environmental monitoring, motor-vehicle tail-gas detections, demand is extensive at home.Particularly, in trace gas on-line monitoring field, also lack a kind of method of simple and effective.Cavity attenuation and vibration technique is as a kind of feasible trace gas on-line monitoring, be high resolving power, the high precision absorption spectroscopy techniques growing up based on absorption spectrum in passive cavity chamber, it mainly obtains the absorption coefficient of medium in chamber by measuring the ring-down time of light in high reflection cavity.In cavity attenuation and vibration technique and chamber, absorb, the difference of long-range absorption spectroscopy techniques be its do not pay close attention to light intracavity reflecting number of times number, and the ring-down time of concern light in chamber, the ratio of an intensity, avoided the fluctuation amplitude of laser intensity to the impact of measuring, thereby the precision of measuring improves greatly, but it is subordinated to direct absorption spectroscopy techniques from essence.
The development of cavity attenuation and vibration technique is for measuring the reflectivity of optical mirror plane at first, and along with the development of cavity attenuation and vibration technique, being applied to trace gas analysis is the direction of current cavity attenuation and vibration technique development.Domestic existing Duo Jia unit is studied chamber dying oscillation absorption spectrum technology, but all also at the experimental stage.Swing during chamber technology realizes declining, the pattern matching problem of LASER Light Source and optical resonator is key wherein, by checking patent and literature survey, find, the optical resonator that the experimental provision of setting up in most research or the prototype machine of attempting researching and developing are used all adopts straight cavity configuration, because optical maser wavelength scanning is because length scanning limited bandwidth, sometimes cannot realize mating of light source and optical resonator, therefore existing device is all the chamber progress line scanning of modulation vibration to optical resonator that adopts PZT, thereby reaches the object with LASER Light Source pattern match.For straight cavity configuration, PZT is installed on a high catoptrics eyeglass, due to the outgoing that will avoid laser at center of lens, therefore increased the difficulty of cavity installment and debugging.
Summary of the invention
The object of invention: for the trace gas on-line analysis device that declines and swing based on chamber that a kind of control accuracy is good, easy for installation is provided.
In order to reach as above object, the present invention takes following technical scheme:
A trace gas on-line analysis device that declines and swing based on chamber, is characterized in that, comprises the laser instrument, optoisolator, optical resonator, the laser detector that distribute successively; Optical resonator is the straight chamber that reflective concave surface mirror is equipped with at two ends, on straight chamber, has air intake opening and gas outlet, prevents that optoisolator that laser reflection returns laser instrument is between laser instrument and optical resonator.
The further technical scheme of the utility model is, is surrounded by one layer of heat preservation layer on described optical resonator, and there are temperature sensor and heating arrangement in heat-insulation layer below.
The further technical scheme of the utility model is, each own flow sensor on the air intake opening in described straight chamber and gas outlet.
The further technical scheme of the utility model is, described laser instrument is the Distributed Feedback Laser that output wavelength can be modulated by electric current.
The further technical scheme of the utility model is, the air intake opening in described straight chamber or gas outlet connection vacuum extractor.
The further technical scheme of the utility model is, also comprises temperature control modules, and described laser instrument, temperature control modules, laser detector connect CPU separately.
The further technical scheme of the utility model is, described optoisolator model is I-15-B4.
The further technical scheme of the utility model is, described CPU also connects time set.
The further technical scheme of the utility model is, described CPU also connects STM32f103 chip.
Adopt as above the utility model of technical scheme, with respect to prior art, have following beneficial effect:
This device is by the long pattern match of carrying out laser instrument and resonator cavity that regulates in the modulation of integrated application optical maser wavelength, optical resonator destructing design and temperature control chamber, cancelled the long modulating part in chamber of acoustooptic switch and PZT, simplify the structure, improved system reliability,, can realize the trace gas on-line continuous monitoring in the fields such as industrial process and environmental monitoring.
Accompanying drawing explanation
In order to further illustrate the present invention, below in conjunction with accompanying drawing, further describe:
Fig. 1 declines in chamber and swings trace gas analysis apparatus structure composition;
Fig. 2 declines in chamber and swings trace gas analysis ultimate principle;
Wherein: 1. laser instrument; 2. optical isolator; 3. optical resonator; 4. heat-insulation layer; 5. laser detector.
Embodiment
Below in conjunction with accompanying drawing, embodiments of the invention are described, embodiment is not construed as limiting the invention:
A trace gas on-line analysis device that declines and swing based on chamber, is characterized in that, comprises the laser instrument, optoisolator, optical resonator, the laser detector that distribute successively; Optical resonator is the straight chamber that reflective concave surface mirror is equipped with at two ends, on straight chamber, has air intake opening and gas outlet, prevents that optoisolator that laser reflection returns laser instrument is between laser instrument and optical resonator.The technique effect that this place at least can realize is laser can be injected to optical resonator, and detects its decay with detecting device, except detectable concentration, can also detect optical resonator inner the blocking capability of the material that fills to laser energy.
On described optical resonator, be surrounded by one layer of heat preservation layer 4, there are temperature sensor and heating arrangement in heat-insulation layer below.The structure at this place is the accurate function of temperature control realizing optical resonator.
Each own flow sensor on the air intake opening in described straight chamber and gas outlet.The technique effect that structure rose at this place is to detect flow, can be also flow measurement device, can effectively be controlled at the number of the material of optical resonator inside.
Described optical resonator is quartz glass, and expansion coefficient is at 5.5*10
-7pC, its two ends are plano-concave mirrors.Described laser instrument is the Distributed Feedback Laser that output wavelength can be modulated by electric current.
The air intake opening in described straight chamber or gas outlet connect vacuum extractor.The structure at this place can be founded a complete pure environment to put into the gas that needs threading, reduces external interference as far as possible.
Described laser instrument, optoisolator, optical resonator, laser detector connect CPU separately.The CPU at this place can be also computer or central control system, and it connects attemperating unit.
Described optoisolator model is I-15-B4.The isolator at this place can be purchased from American I SOwave company.
Described CPU also connects time set.Described CPU also connects STM32f103 chip.Be different from the gas analyzing apparatus of general cavity attenuation and vibration technique, declining and swing trace gas analysis device in the chamber that the utility model relates to is by the long pattern match of carrying out laser instrument and resonator cavity that regulates in the modulation of integrated application optical maser wavelength, optical resonator structures design and temperature control chamber, thereby cancelled the long modulation module of expensive acoustooptic switch and PZT chamber, reached the object of simplified structure, raising system reliability.
Whole device is processed with control module and is formed by laser instrument, optoisolator, optical resonator, laser detector, temperature control module, signal.The control module at this place can be exchanged with CPU.The course of work of device is as follows:
Laser instrument is exported a branch of parallel laser through collimation lens, and laser enters optical resonator via optoisolator is laggard, and optical resonator is the straight chamber that high reflective concave surface mirror is equipped with at two ends, has air intake opening and gas outlet on chamber.Optoisolator, between laser instrument and optical resonator, prevents that laser reflection from returning laser instrument.Because two ends in chamber are high reflective concave surface mirrors, laser can produce multiple reflections in chamber, after every secondary reflection, at concave mirror place, can spill part light, when laser forms after stable resonant oscillation in chamber, goes out the laser beam of stable output to laser detector at concave mirror.When detecting device detects laser, surpass after certain threshold value, by signal processing and control module, send control signal, by current-modulation, turn-off laser instrument.Now the laser in chamber carrys out back reflective between two chamber mirrors, every secondary reflection, and light intensity all can weaken because of the absorption of chamber mirror transmission, diffraction, sample, and laser detector may detect transmitted light intensity over time, and device principle of work is as shown in Figure 2.If the reflectivity of known two chamber mirrors, in this chamber, be filled with gas absorption sample, just can be by measuring the absolute absorption of measuring sample die-away time, it is different from common absorption spectroscopy techniques, it not the absorption of directly measuring sample, but measure relative ring-down time, therefore can effectively avoid the amplitude fluctuation noise of light source, simultaneously because laser comes and goes multiple reflections in resonator cavity, equivalence absorbs Cheng Feichang large (can reach tens even hundreds of kilometer), thereby has very high measurement sensitivity.
Theoretical according to multiple-beam interference, laser is in chamber during multiple reflections, and as long in fruit caving and sharp light wavelength can not be mated, and will cause endovenous laser energy attenuating because of interference, and the laser of laser instrument can not enter optical resonator by efficient coupling.Therefore the pattern matching problem of laser source wavelength and optical resonator must solve.Common way is, at a high reflection mirror sheet, PZT crystal oscillator pottery is installed, and by exciting PZT to vibrate to carry out chamber long scan according to certain frequency, thereby reaches the object of optical maser wavelength and cavity length matching.PZT is installed on high reflective mirror and need to guarantees that PZT does not stop incident and the outgoing of laser, also to guarantee that PZT can, because of making eyeglass inclination etc. cause the transverse mode imbalance of optical resonator, therefore not used PZT to adjust chamber greatly to increase the installation of optical resonator and adjusted chamber difficulty in when vibration simultaneously.
The utility model is by having solved cleverly frequency mode matching problem by methods such as the modulation of integrated application optical maser wavelength, the long adjustings of optical resonator structures design and temperature control chamber.
During due to single employing optical maser wavelength modulator approach, the wavelength modulation range of semiconductor laser is limited, generally at tens nm, and be generally near-infrared band for gasmetry laser instrument, wavelength is more than 700nm, if when therefore the longitudinal mode resonance point of effective cavity length and coupling distance differs hundreds of nm, cannot complete frequency mode by wavelength-modulated and mate.The installation of optical resonator cannot make effective cavity length error be controlled between tens nm, and therefore single employing optical maser wavelength modulator approach cannot achieve the goal.
The utility model adopts common quartz glass as cavity material (also can adopt other materials with suitable coefficient of thermal expansion and contraction as cavity material), when chamber length surpasses 30cm, if when temperature variation surpasses 20 degrees Celsius, change of cavity length will be over 2000nm.When single employing optical maser wavelength modulator approach cannot reach frequency mode coupling, it is long that the temperature setting that constantly changes cavity by temperature control modules changes chamber, until use optical maser wavelength modulator approach can reach frequency mode coupling, by Temperature Setting now, be cavity temperature, cavity temperature general control is at 40 to 60 degrees Celsius.
By temperature, control the frequency mode matching problem that not only can solve LASER Light Source and optical resonator, can also avoid ambient temperature to change the impact on intracavity gas absorptivity.
Specific implementation is usingd minor amount of water as detecting target.It is that the DFB tunable laser of 1823nm is LASER Light Source that device is selected centre wavelength.It is material that optical resonator be take common practical glass, chamber interior diameter 20mm, and the long 300mm in chamber, wall thickness 8mm, two ends are plano-concave high reflection mirror sheets, lens surface is coated with the infrared highly reflecting films that centre wavelength is 1823nm, the about 100nm of bandwidth, reflectivity is greater than 99.99%.Detecting device adopts the near infrared InGaAs photodetector of Thorlabs company.Optical resonator is wound around heater strip outward, external application Metal Packaging.Between LASER Light Source and optical resonator, adopt the optical isolator of a 30dB.
It is the basis of whole system co-ordination that signal is processed with control module, and the tuning current that it mainly completes laser instrument injects; The amplification of laser detector output signal, filtering, AD conversion; The Detection & Controling of the outer temperature signal of optical resonator; Several large functions such as the shutoff of LASER Light Source, functions of modules module as shown in Figure 3.Whole module adopts STM32f103 chip to realize, and this chip can be realized 72M clock frequency, can realize the clock control of ns level, can turn-off in time LASER Light Source, guarantees the exponential decline that light decay swings.Compare with the light ring-down time of ms level in addition, the clock control precision of ns level can also realize the ring-down time of degree of precision and measure.This chip also possesses 12 AD inputs in addition, and peripheral functionality is very abundant, can realize module required function.
After optical resonator has assembled, by cross imaging method, two high reflective mirror furnishings are parallel, and minute surface is perpendicular to optical axis.Optical resonator is heated and be controlled at 40 degree, control accuracy 0.3 is spent.Now allow parallel laser along optical axis incident, observe the output signal of laser detector, and record this signal intensity.Then successively according to the temperature of the interval rising resonator cavity of 1 degree, and the laser detector output signal strength that record is each after heating up.Due to the rising of temperature, the chamber length of optical resonator will constantly change, and when changing to LASER Light Source, mate, and when laser produces complete resonance in chamber, the signal intensity that laser detector detects is maximum.Therefore the laser output intensity of relatively more each record, by optical resonator Temperature Setting on that temperature value of output signal maximum.Afterwards, LASER Light Source is carried out to wavelength-modulated, to guarantee measuring accuracy and realize at utmost resonance in modulated process.
More than show and described ultimate principle of the present invention, principal character and advantage of the present invention.Those skilled in the art should understand the present invention and not be restricted to the described embodiments; that in above-described embodiment and instructions, describes just illustrates principle of the present invention; 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 all fall in claimed scope.
Claims (10)
1. a trace gas on-line analysis device that declines and swing based on chamber, is characterized in that, comprises the laser instrument, optoisolator, optical resonator, the laser detector that distribute successively; Optical resonator is the straight chamber that reflective concave surface mirror is equipped with at two ends, on straight chamber, has air intake opening and gas outlet, prevents that optoisolator that laser reflection returns laser instrument is between laser instrument and optical resonator.
2. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that, is surrounded by one layer of heat preservation layer (4) on described optical resonator, and there are temperature sensor and heating arrangement in heat-insulation layer below.
3. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that each own flow sensor on the air intake opening in described straight chamber and gas outlet.
4. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that, described optical resonator is quartz glass, and expansion coefficient is at 5.5*10
-7its two ends of PC are plano-concave mirrors.
5. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that, described laser instrument is the Distributed Feedback Laser that output wavelength can be modulated by electric current.
6. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 3, is characterized in that, the air intake opening in described straight chamber or gas outlet connect vacuum extractor.
7. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that, also comprise temperature control modules, described laser instrument, temperature control modules, laser detector connect CPU separately.
8. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 1, is characterized in that, described optoisolator model is I-15-B4.
9. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 7, is characterized in that, described CPU also connects time set.
10. a kind of trace gas on-line analysis device that declines and swing based on chamber as claimed in claim 7, is characterized in that, described CPU also connects STM32f103 chip.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201320710426.7U CN203745374U (en) | 2013-11-12 | 2013-11-12 | Cavity ring-down-based online trace gas analysis device |
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| CN201320710426.7U CN203745374U (en) | 2013-11-12 | 2013-11-12 | Cavity ring-down-based online trace gas analysis device |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104515742A (en) * | 2014-12-17 | 2015-04-15 | 中国科学院长春光学精密机械与物理研究所 | Method for improving cavity ring-down time measurement accuracy |
| CN106483069A (en) * | 2015-08-26 | 2017-03-08 | 西安泰戈分析仪器有限责任公司 | Trace gas on-line analyses device based on cavity attenuation and vibration technique |
| CN106645024A (en) * | 2016-12-17 | 2017-05-10 | 浙江泰林生物技术股份有限公司 | TDLAS-based wide-range detector for concentration of gasified H2O2 |
| CN109244820A (en) * | 2018-09-25 | 2019-01-18 | 南京先进激光技术研究院 | A kind of temperature control optical resonator automatic freqauency stabilization method and device |
| CN110031410A (en) * | 2019-04-15 | 2019-07-19 | 中国科学院光电研究院 | A kind of laser, which declines, swings detection device |
| CN111879705A (en) * | 2020-08-07 | 2020-11-03 | 中国科学技术大学先进技术研究院 | Mixed gas measuring method, mixed gas measuring system and storage medium |
-
2013
- 2013-11-12 CN CN201320710426.7U patent/CN203745374U/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104515742A (en) * | 2014-12-17 | 2015-04-15 | 中国科学院长春光学精密机械与物理研究所 | Method for improving cavity ring-down time measurement accuracy |
| CN104515742B (en) * | 2014-12-17 | 2017-01-18 | 中国科学院长春光学精密机械与物理研究所 | Method for improving cavity ring-down time measurement accuracy |
| CN106483069A (en) * | 2015-08-26 | 2017-03-08 | 西安泰戈分析仪器有限责任公司 | Trace gas on-line analyses device based on cavity attenuation and vibration technique |
| CN106645024A (en) * | 2016-12-17 | 2017-05-10 | 浙江泰林生物技术股份有限公司 | TDLAS-based wide-range detector for concentration of gasified H2O2 |
| CN109244820A (en) * | 2018-09-25 | 2019-01-18 | 南京先进激光技术研究院 | A kind of temperature control optical resonator automatic freqauency stabilization method and device |
| CN110031410A (en) * | 2019-04-15 | 2019-07-19 | 中国科学院光电研究院 | A kind of laser, which declines, swings detection device |
| CN111879705A (en) * | 2020-08-07 | 2020-11-03 | 中国科学技术大学先进技术研究院 | Mixed gas measuring method, mixed gas measuring system and storage medium |
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Granted publication date: 20140730 Termination date: 20191112 |