CN205941327U - Low -cost reflective absorption cell of gaseous optical absorption of high accuracy - Google Patents
Low -cost reflective absorption cell of gaseous optical absorption of high accuracy Download PDFInfo
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- CN205941327U CN205941327U CN201620867800.8U CN201620867800U CN205941327U CN 205941327 U CN205941327 U CN 205941327U CN 201620867800 U CN201620867800 U CN 201620867800U CN 205941327 U CN205941327 U CN 205941327U
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- collimater
- light
- faraday rotation
- rotation mirror
- air chamber
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Abstract
The utility model discloses a low -cost reflective absorption cell of gaseous optical absorption of high accuracy belongs to the gaseous optical absorption's of near -infrared technical field. It relates to optical sensor, utilize the light of the specific wavelength of narrowband laser instrument output oblique wave scanning formula, reach collimater A through the circulator, the collimater will be bare the parallel and be jetted out, collimater B reachs, collimater B reachs the faraday rotation mirror through connecting optic fibre, the faraday rotation mirror is with the the polarization direction rotatory 90 of light, catch through collimater B, return collimater A, collimater A reachs the circulator again, then carry out photoelectric conversion, it detects to carry out intensity behind the letter after obtaining changing, because the parallel characteristic of collimater and let light expand the characteristic of restrainting make light the outgoing and return power and strengthen greatly, the SNR has been improved, the problem of interference of light has been solved in the joining of faraday rotation mirror, has improved the precision of detectable greatly.
Description
Technical field
The utility model is related to design based on the distributed optical fiber methane sensing system of high accuracy it is adaptable to various optics
Reflective air chamber, more particularly, to detect the system of methane concentration using reflective.
Background technology
In infrared methane sensor, the design of air chamber structure is generally related to the performance quality of this sensor, so, gas
Room is one of critical component of sensor, is also the key of whole system, is related to the precision of this system, sensitivity and stable
Property.Because methane gas produced by accident and emergency causes to normal productive life in production and living environment
The methane gas producing in very big harm, especially mine, it is the important composition gas causing mine gas explosion.With
Expanding economy, the detection to methane gas is put forward higher requirement, and reflective methane transducer is affected by environment little, spirit
Sensitivity is high, and fast response time the advantages of with low cost, becomes the hot topic of infrared gas sensor area research.
The general principle of reflective air chamber is that light beam got by laser instrument, reaches speculum through collimater, and speculum exists
Reflect light back into, then reach optical-electrical converter through collimater.Concrete principle is as shown in Figure 1.
The reflective air chamber in White pond
White pond basic structure is as shown in Figure 2
White pond is a kind of short-range multiple reflections formula air chamber, mainly by one big two little 3 confocal concave spherical mirror structures
Become, both can realize the transmission of repeatedly turning back of the light velocity, the angle of divergence will not be exaggerated and be beneficial in the transmission can to control light beam again
Receive.
Its general principle is three center of curvature identical spherical concave mirrors, and little mirror is respectively A, A ', identical, big mirror
For B.Little mirror A, A ' are mounted at grade, and big mirror B is in little mirror A, A ' opposite, and center of curvature C of big mirror BBFall
Little mirror A, the centre in A ' concave surface, and A, A ' on same vertical plane, little mirror A, center of curvature C of A 'AAnd CA' fall in the concave surface of B
Interior, CAAnd CA' with respect to the distribution of big mirror B concave surface Central Symmetry.Distance in the middle of little mirror A, A ' and big mirror B is the curvature of spherical mirror
Radius.Because sphere curvature radius is two times of focal length, therefore when incident illumination is on little mirror A, the reflection through excessive mirror B, can
The light reflecting from A is converged to A ', and reflects White pond from A ', this is triple reflection.
White pond shortcoming：
1) manufacture difficulty is big, adjusts difficulty big.Focal length due to three mirror contact lens in White pond must be strictly equal, from manufacture
Technique on for be difficult to, and need adjust light path, adjust need specialty instrument and personnel could calibrate
2) practical cost is high, is not suitable for universal application.On the market have ready-made White pond, but its price is excessively frightened
People is it is difficult to be applied to practical matter it is impossible to commonly used.
3) it is not suitable for various environment, durability degree is low.White pond is due to being that minute surface is embedded in air chamber, severe at some
In environment, such as vibrations etc. are difficult to stablize；And if gas is corrosivity or bad environments, durability degree is very low.
Transmission-type air chamber
Transmission-type air chamber principle is as shown in Figure 3
Transmission-type air chamber process is simple, with low cost, it is suitable for various occasions.The light sending from laser beam emitting device enters
Cross air chamber arrival photoelectric receiving arrangement to be changed, reach the purpose of detection.
The shortcoming of transmission-type air chamber
1) transmission-type light path is short, and accuracy of detection is not high, and sensitivity is low.According to absorbing rule Bill's-Lang Bo law of gas,
The length of air chamber is longer, then detectable precision is higher, and sensitivity is also extremely low, practical application difficult to reach application standard.
2) distance transmission-type air chamber high cost is it has not been convenient to assembling and using.With respect to high-precision detection, need to use
The air chamber of distance, but manufacture air chamber (1m) high cost of distance, and be inconvenient to assemble.
Reflective air chamber
The principle of reflective air chamber is as shown in Figure 4
According to the emission principle of light, light is vertically driven in air chamber reflective air chamber, is then passed through speculum reflection, along
Backtracking, so that light path increases 2 times, improves accuracy of detection and sensitivity.
The shortcoming of reflective air chamber
1) there is the interference problem of light.Due to the fluctuation of light, the light of reflection can interfere with the light of transmission, formed and interfere
Striped, thus affect accuracy of detection even cannot normal work, and air chamber is longer, and interference fringe is more it is impossible to exclusion is interfered
Impact, leads to its precision to be greatly reduced.
2) collimation of light cannot be ensured, the light reflecting not necessarily can be entirely reflected in the detection in loop.And
And the decay of light can be led to, have impact on accuracy of detection.Also it is difficult with circumstances.
Content of the invention
The utility model remains unchanged by the way of reflective.Solve going out of the interference problem of light and light in reflective air chamber
The parallel problem injected, can easily be on the actual application in various practical application.It greatlys save into
This, facilitate substantial amounts of Productive statistics to use.
The utility model is a kind of reflective air chamber of the low cost that can apply to various occasions, which solves tradition anti-
Penetrate the interference that there is light of formula air chamber, substantially increase detectable precision, and solve the collimation of light
Problem, can be achieved with high-precision detection with shorter distance.
The utility model design principle：
1) according to Beer-Lambert law, when a branch of light intensity is I0Directional light by the air chamber containing methane gas when, such as
Fruit optical signal covers the absorption line of methane gas, then transmission or reflection light intensity decays.Output intensity I (λ) and input light
Strong I0(λ), the relation between gas concentration C is：
Wherein, αλThe absorption coefficient in a length of λ of light wave for the methane gas, L is the length absorbing path.Derivation can obtain；
Then
As can be seen here, the length of air chamber decides sensitivity and the precision of the gas that can detect.Lengthen the length of air chamber
Sensitivity and the precision of system can be improved, but too long of air chamber is unfavorable for assembling, cost is slightly higher；White pond cost is too high, various
Environment is inapplicable.Have suitable length only and precision is only the requirement of application.
2) due to being reflective structure, the light of the reflective light sending and return, can cause interference, lead to precision to drop
Low or cannot complete detect.
Faraday rotation mirror is the speculum that can rotate 90 ° the polarization direction of light, due to the initial polarization side of light
To being shear wave, and laser instrument send be the direction of vibration single vibration direction vertical with optical propagation direction shear wave, when light warp
When crossing faraday rotation mirror, the direction of vibration of light deflects 90 ° of returns, thus cannot form interference, can be very good to meet height
The detection of precision requires.
Structure of the present utility model
This high-precision reflective absorption cell, by circulator, anterior protection end, collimater A, air chamber cavity, collimater B,
Faraday rotation mirror, rear end protective cover, connect optical fiber and single-mode fiber.
The circulator of 1650nm selected by circulator, and its loss is minimum.
Anterior protective case is used for connecting and protecting collimater, and ensures the vertical angle of collimater so as to have good
Stability and security.
The light that collimater A is used for laser instrument to dissipate converges, and parallel launches and carry out expanding the horizontal stroke increasing light
Section, increases the contact area of light and gas, then parallel and be accurately transmitted into collimater B receive.
Air chamber cavity is made up of gas infiltration set and protection overcoat, for protecting overall air chamber structure.
Collimater B is used for receiving the light beam that collimater A converges, and is transmitted to faraday rotation mirror.
Faraday rotation mirror is used for rotating 90 ° the direction of vibration of light, and returns along Yuan Lu, solves the interference of light
Problem.
End protective cover is used for protecting collimater and faraday rotation mirror for protective case afterwards.
Connect optical fiber to be used for connecting collimater and faraday rotation mirror.
Single-mode fiber is used for the transmission of light.
The beneficial effects of the utility model：
The utility model successfully solves conventional reflective air chamber due to interfering the impact of amplitude fluctuation after opto-electronic conversion
The detection causing is inaccurate, for all kinds of detecting systems, improves the precision of its detection and the unfailing performance of system well.
The utility model adopts dual collimator to focus, optical path adjusting measure that need not be complicated, fixing after the completion of then can be direct
Use, improve the signal to noise ratio of return signal, be adapted to the application of various environment, can keep good in various rugged environments
Good performance.
The utility model is with low cost, but practical application is the most extensive, can be with large batch of production and application.
Brief description
Fig. 1 is the overall detailed structure view that this other optical absorbs reflective absorption cell.
Fig. 2 is the basic structure in White pond.
Fig. 3 is the basic structure of transmission-type air chamber.
Fig. 4 is the basic structure of reflective air chamber.
Fig. 5 is air chamber cavity cross-section figure.
Fig. 6 is the entire block diagram of this system.
Fig. 7 is that this system connects the final result producing of common reflective air chamber.
Fig. 8 is that this system connects the final result producing of the reflective air chamber after improving utility model.
Specific embodiment
Laser emitter sends the laser after modulation (having scan-type, have sinusoidal superposing type)；The laser sending passes through standard
The straight parallel injection of device A, reaches collimater B, and collimater B is passed through to connect optical fiber, and light is got to faraday rotation mirror, and faraday is revolved
The direction of vibration of light is rotated 90 ° by tilting mirror, is reflected back collimater B, and parallel light is got by collimater B again, reaches collimater A, accurate
Straight device A receives light, reaches photoelectric conversion device by circulator.
Wherein, connection optical fiber, Transmission Fibers, collimater and circulator need from the detection corresponding wavelength of gas, such as first
The corresponding absworption peak wavelength of alkane is 1645.5nm, then the connection optical fiber selected, Transmission Fibers, and collimater and circulator all should select
Corresponding passive device with 1645.5nm wavelength.
The design at front-end protection end, needs convenient for assembly, is easy to the use of various occasions, and will protect air chamber body and standard
Straight device A
Air chamber cavity as shown in figure 5, head and afterbody have the assembly space of collimater A and collimater B, for the ease of dislike
The use of bad environment, using carving conjunction welded type, is needing two collimator-alignment of suitable regulation, difficulty at first
Substantially reduce.
The design of end protective cover afterwards, its object is to protect collimater B and faraday rotation mirror, is also convenient for assembling simultaneously
Using air chamber of the present utility model, devise an optical fiber methane gas concentration detection system, including light source, driving
Module, temperature control module, circulator, optical signal link, reflective air chamber, optical-electrical converter, small-signal amplification module, module of differentials
The units such as block, Signal-regulated kinase, analog-to-digital conversion module, processor.Structured flowchart is as shown in Figure 6.
Methane adsorption peak have selected the wavelength of 1645.5nm, is detected by the way of scanning.Swashing from 1645nm
Light device, the mode being scanned with oblique wave, sweep limits, from 1645nm to 1646nm, completes wavelength modulation.
Temperature control module adopts negative feedback control, controls the refrigerator that laser instrument carries to carry out by sense of current and size
Heat or freeze, thus keeping the temperature stabilization of laser instrument reasonably interval at one.Optical signal after modulation through circulator,
Transmission Fibers, reflective air chamber, according to Beer-Lambert law produce decay, then by collimater B reach faraday rotation mirror,
Produce decay again through air chamber, be then passed through circulator and return, be changed into the ultra-weak electronic signal of microampere order through optical-electrical converter.
Amplified module makes electric signal be amplified to the level that can carry out signal transacting, then through derivative module, Signal-regulated kinase and
Analog-to-digital conversion module, obtains the digital quantity that processor can be processed.
Two ways is employed for reflective air chamber contrast, a kind of is to connect the speculum of common corresponding wavelength such as
Shown in Fig. 7, second is that to connect faraday rotation mirror as shown in Figure 8.
As seen from the figure, amplitude fluctuations after the opto-electronic conversion that normal mirror is brought are which overcomed due to the interference of light
Interference, improves the precision of system.
Claims (4)
1. a kind of high-precision low cost other optical absorb reflective absorption cell it is characterised in that：Including circulator, anterior guarantor
Shield end, collimater A, air chamber cavity, collimater B, faraday rotation mirror, rear end protective cover, connection optical fiber and single-mode fiber；
The circulator of 1650nm selected by circulator, and anterior protective case is used for connecting and protecting collimater, and ensures hanging down of collimater
Squareness is so as to have good stability and security；
The light that collimater A is used for laser instrument to dissipate converges, and parallel launches and carry out expanding the cross section increasing light,
Increase the contact area of light and gas, then parallel and be accurately transmitted into collimater B receive；
Air chamber cavity is made up of gas infiltration set and protection overcoat, for protecting overall air chamber structure；
Collimater B is used for receiving the light beam that collimater A converges, and is transmitted to faraday rotation mirror；
Faraday rotation mirror is used for rotating 90 ° the direction of vibration of light, and returns along Yuan Lu；
End protective cover is used for protecting collimater and faraday rotation mirror afterwards；
Connect optical fiber to be used for connecting collimater and faraday rotation mirror；
Single-mode fiber is used for the transmission of light.
2. a kind of other optical of high-precision low cost according to claim 1 absorbs reflective absorption cell, and its feature exists
In：Narrow band laser exports the light that oblique wave scanning is specific wavelength, reaches collimater A through circulator, collimater is by parallel light
Project, reach collimater B, collimater B reaches faraday rotation mirror through connecting optical fiber, and faraday rotation mirror is by the polarization side of light
To rotating 90 °, get through collimater B, return to collimater A, collimater A reaches circulator again, then carry out opto-electronic conversion,
Carry out intensity detection, because the parallel nature of collimater makes the outgoing of light and returns power greatly greatly after letter after being changed
By force, improve signal to noise ratio；The addition of faraday rotation mirror makes return light because interference brings in the signal after opto-electronic conversion
Amplitude disturbances disappear, thus substantially increasing detectable precision.
3. a kind of other optical of high-precision low cost according to claim 1 absorbs reflective absorption cell, and its feature exists
In：Air chamber, by the way of reflective, is used as speculum with faraday rotation mirror, solves the intensity inspection that the interference of light causes
Amplitude fluctuation problem in survey, improves the precision of detection.
4. a kind of other optical of high-precision low cost according to claim 1 absorbs reflective absorption cell, and its feature exists
In：Two ends all adopt collimater so that the incidence of parallel light and outgoing, and have, to light, the effect expanding, and increase and gas
Contact area, its excellent stability, substantially increase the signal to noise ratio of detecting system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620867800.8U CN205941327U (en) | 2016-08-11 | 2016-08-11 | Low -cost reflective absorption cell of gaseous optical absorption of high accuracy |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620867800.8U CN205941327U (en) | 2016-08-11 | 2016-08-11 | Low -cost reflective absorption cell of gaseous optical absorption of high accuracy |
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| CN205941327U true CN205941327U (en) | 2017-02-08 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201620867800.8U Expired - Fee Related CN205941327U (en) | 2016-08-11 | 2016-08-11 | Low -cost reflective absorption cell of gaseous optical absorption of high accuracy |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110031034A (en) * | 2019-03-06 | 2019-07-19 | 北京航天易联科技发展有限公司 | A kind of demodulation of optic fiber grating wavelength and calibration system and method |
-
2016
- 2016-08-11 CN CN201620867800.8U patent/CN205941327U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110031034A (en) * | 2019-03-06 | 2019-07-19 | 北京航天易联科技发展有限公司 | A kind of demodulation of optic fiber grating wavelength and calibration system and method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170208 Termination date: 20170811 |