CN204086122U - A kind of atmospheric visibility pick-up unit based on cavity attenuation and vibration technique - Google Patents
A kind of atmospheric visibility pick-up unit based on cavity attenuation and vibration technique Download PDFInfo
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Abstract
The utility model belongs to Fibre Optical Sensor and visibility measurement technical field, particularly a kind of atmospheric visibility pick-up unit based on cavity attenuation and vibration technique.This device comprise set gradually light source, import optical fiber, resonator cavity, derivation optical fiber, photodetector and calculate the data processing unit being detected sample visibility value for light loss data being carried out.Data processing unit draws the loss of light wave in resonator cavity according to the characteristic of resonator cavity, is finally determined the visibility numerical value of tested sample by light loss.The apparatus structure that the utility model proposes is compact, method is easily understood is convenient to implement, and the precision and the detection perform that greatly provide the detection of tested sample visibility are stablized, and are applicable to the fields such as highway communication, navigation, aviation, atmosphere pollution monitoring.
Description
Technical field
The utility model belongs to Fibre Optical Sensor and visibility measurement technical field, particularly a kind of atmospheric visibility pick-up unit based on cavity attenuation and vibration technique.
Background technology
Visibility is an important atmospheric optical properties parameter, is also the important meteorologic parameter affecting people's daily life and trip.In fields such as highway communication, aviation, navigation, atmosphere pollution monitorings, there is the demand to visibility measurement.Definition for visibility has various ways, and the definition of wherein comparing science is so-called meteorological visible visual range.Meteorological visible visual range is defined as: the directional light that the incandescent lamp that colour temperature is 2700 Kelvins sends is propagated in an atmosphere, its power attenuation is initial value 5% time the distance propagated.
Current visibility instrument mainly contains transmission-type visibility meter, diffuse transmission type visiometer, laser radar visibility meter, visiometer etc. based on image procossing.
In one of first technology: transmission beam method
When light wave is propagated in an atmosphere, various solia particle contained in air and fine droplet can cause scattering and the absorption of light wave, and concerning the observer of certain fixed-direction, the effect of scattering and absorption all shows as the decay of the luminous power received.Therefore, by measuring the change of luminous power, atmospheric visibility value can be obtained, as shown in Figure 3 a.This method is the direct measurement of the definition based on " meteorological visible visual range ", and it is the most reliable that institute obtains visibility numerical value.The problem of transmission beam method is to measure difficulty, when visibility good, needs the light path of several kilometers that light wave can be allowed to produce and decays more significantly.For the surveying instrument of reality, light path only about a meter, thus needs high measurement dynamic range.Consider the factors such as the contamination by dust of the direction mismatch between light source power fluctuation, detector efficiency change, optical light source and detector, optical window, this principle may be utilized in fact hardly to produce high-precision visiometer.
In first technology two: scattering method
The scattering of air to various solid, liquid particulates contained in the loss of light wave mainly air causes, and therefore, by measuring the power of scattered light, can extrapolate atmospheric visibility, as shown in Figure 3 b.The technical difficulty of scattering method will, lower than transmission beam method, be the mainstream technology that current visibility is measured.But scattering method is a kind of indirect inspection based on certain approximation relation, the in fact relation of the value that measures of scattering method and actual visibility not strictly one_to_one corresponding.For majority of case, the measured value of scattering method is the good approximation of true visibility, but for the air be heavily polluted, the model difference used due to its composition and scattering method is comparatively large, thus can produce larger deviation.In addition, the problems such as scattering method also exists such as light source power fluctuation, detector efficiency changes, the contamination by dust of optical window.
In first technology three: laser radar method
Laser radar method is also the backscattering of certain scattering method, measuring beam.Its advantage is the visibility data can measured in a big way, and shortcoming is expensive, if only for the measurement of visibility, is huge waste.Meanwhile, also there is the problems such as light source power fluctuates, the contamination by dust of optical window.
In first technology four: image treating
Image treating defines based on the another kind of visibility: under well-lighted condition, and the observer of normal vision can see the ultimate range of special pattern clearly.Image treating needs use digital camera simulation human eye, and directly picked-up selected target thing is taken, and image is inputted computing machine.Computing machine carries out analyzing and processing to obtained image again, obtains visibility observed reading.This method needs remote image objects, at some application scenario, such as navigational field, is not to find suitable object.
Utility model content
In order to solve problem existing in background technology, the utility model proposes that a kind of compact conformation, precision are higher, stable performance, be applicable to the atmospheric visibility pick-up unit based on cavity attenuation and vibration technique in the fields such as highway communication, navigation, aviation, atmosphere pollution monitoring.
The technical solution of the utility model is as follows:
Based on an atmospheric visibility pick-up unit for cavity attenuation and vibration technique, it is characterized in that: comprise the light source, resonator cavity, the photodetector that set gradually and calculate for light loss data being carried out the data processing unit being detected sample visibility value.
Above-mentioned detection device also comprises the importing optical fiber be arranged between light source resonant cavity and the derivation optical fiber be arranged between resonator cavity and optical detector.
Above-mentioned resonator cavity is optical resonator; Importing collimating apparatus is provided with between described light source and optical resonator; Derivation collimating apparatus is provided with between described optical resonator and photodetector.
Above-mentioned resonator cavity is fiber resonance cavity; Described fiber resonance cavity comprises the first coupling mechanism, special optical fiber and the second coupling mechanism; Input end and the importing Fiber connection of described first coupling mechanism, the output terminal of the first coupling mechanism is connected with the input end of special optical fiber; The output terminal of described special optical fiber is connected with the input end of the second coupling mechanism; The output terminal of described second coupling mechanism is connected with optical detector respectively at the input end of the first coupling mechanism; Described special optical fiber is for making light wave contact with the sample to be tested in external environment and absorbing.
Above-mentioned special optical fiber is photonic crystal fiber, D-type optical fiber.
Above-mentioned importing optical fiber and derivation optical fiber all adopt single-mode fiber.
The utility model has the advantages that:
1, the optical resonator that utilizes of the present utility model is to the multiple reflections of light wave, substantially increases absorption light path.This makes the detection sensitivity of this system greatly improve.
2, the function of device of the present utility model only parameter with resonator cavity own is relevant, has nothing to do, also have nothing to do with the photoelectric transformation efficiency of detector with light source power, therefore, not easily by the impact of the factors such as light source fluctuation:.
3, the utility model adopts the object of resonator cavity to be increase light path, final measurement be still the loss of light wave in tested sample, because of but the direct measurement of definition based on " meteorological visible visual range ", compared to various indirect inspection, be the most essential and reliable method.
4, the utility model adopts resonator cavity to substantially increase light path, and the distance between two catoptrons can be done very little, thus can make portable set.On volume, not only much smaller than the instrument of direct transmission, also much smaller than the instrument of scattering method.
5, the structure of employing fiber resonance cavity of the present utility model, insensitive to factors such as mechanical vibration, stable performance.
Accompanying drawing explanation
Fig. 1 is structural representation of the present utility model.
Fig. 2 is the resonator cavity Output optical power signal schematic representation in the utility model.
Fig. 3 a is the structural representation of existing transmission-type visibility meter.
Fig. 3 b is the structural representation of existing diffuse transmission type visiometer.
Fig. 4 is Structure and Process block diagram of the present utility model.
Fig. 5 is the structural representation of the utility model embodiment one.
Fig. 6 is the structural representation of the utility model embodiment two.
Reference numeral is as follows:
1-light source, 2-importing optical fiber, 3-resonator cavity, 4-derivation optical fiber, 5-optical detector, 6-data processing unit, 7-importing collimating apparatus, 8-derive collimating apparatus, 9-first coupling mechanism, 10-special optical fiber, 11-second coupling mechanism, 12-acousto-optic modulator.
Embodiment
The utility model provides a kind of atmospheric visibility pick-up unit based on cavity attenuation and vibration technique, the structure of this device is: comprise set gradually light source 1, import optical fiber 2, resonator cavity 3, derive optical fiber 4, be converted to for the light signal that resonator cavity is exported electric signal photodetector 5 and be used for carrying out light loss data to calculate the data processing unit 6 being detected sample visibility value, see Fig. 1.Need special proposition herein: the data processing unit said in this device can be single-chip microcomputer, also can be computing machine computer.Single-chip microcomputer is optional with possessing the chip of certain computing power fast as ARM series processors, the processors such as ARM7, ARM9, ARM11.Computing machine computer can be PC or computer workstation.
Based on said apparatus, application process of the present utility model is described:
Step 1) light signal after resonator cavity attenuation processing launched of photoelectric detector light source;
Step 2) photodetector is by step 1) in light signal be converted to electric signal, and by electric signal transmission to data processing unit;
Step 3) data processing unit is to step 2) in electric signal process, obtain the visibility numerical value of tested sample; Concrete steps are as follows:
Step 3.1) measure the variation relation of output optical signal intensity time of resonator cavity.According to physioptial theory, its relation necessarily has following form:
In formula: τ is ring-down time constant; I
0for the light intensity in t=0 moment; I (t) is light intensity; T is the time;
Step 3.2) according to step 3.1), utilize the time dependent data of light intensity I (t) to calculate ring-down time constant τ, ring-down time constant τ is by the restriction of test substance in the parameter of resonator cavity own and chamber, and concrete calculating formula is as follows:
In formula: n is the refractive index of tested sample, L is that the chamber of resonator cavity is long, and C is the light velocity in vacuum, and R is the reflectivity (supposing equal) of two catoptrons in resonator cavity, and α is the absorption coefficient of tested sample.
Step 3.3) according to step 3.2) in the ring-down time constant τ that obtains, the anti-absorption coefficient releasing tested sample in resonator cavity, physical relationship formula is as follows:
Step 3.4) according to step 3.3) absorption coefficient of tested sample is equivalent to atmospheric extinction coefficient, then according to the relational expression between normal atmosphere visibility and atmospheric extinction coefficient, can determines the relation of visibility and ring-down time constant, as follows:
In formula, V represents the visibility numerical value of tested sample.
In the middle of real work, light source can be the narrow linewidth light source of continuous working, also can be the wide spectrum light source worked in a pulsed fashion, and the former is called continuous light cavity-type BPM visibility Detection Techniques, and the latter is called light-pulse generator cavity-type BPM visibility Detection Techniques.
The principle of work of continuous light source cavity-type BPM is:
(1) the continuous working narrow linewidth light wave of a power stability is injected resonator cavity, guarantee that light source longitudinal mode and a certain longitudinal mode of resonator cavity match, the luminous power of resonator cavity stable output;
(2) turn off light source rapidly, make the luminous power of injection resonator cavity be 0, now, the output power of resonator cavity can not become 0 immediately, but has an attenuation process (cavity-type BPM process);
(3) measure and record this optical power attenuation process, therefrom extracting damping time constant τ;
(4) according to damping time constant τ, anti-release cavity loss α, and calculate visibility V to be measured further.
The pulsed light source strength principle of work of swinging that declines is
(1) resonator cavity is injected in a light pulse;
(2) light pulse is through resonator cavity, roundtrip between two catoptrons of resonator cavity;
(3) light pulse also has sub-fraction through chamber mirror at every turn and exports while being reflected by chamber mirror, forms the pulse train of an amplitude taper;
(4) detect and record this pulse train, therefrom extracting damping time constant τ;
(5) according to damping time constant τ, anti-release cavity loss α, and calculate visibility V to be measured further.
According to the above-mentioned description to apparatus and method, existing utility model people provides the embodiment based on two kinds of different cavity resonator structures, and these two kinds of embodiments all can be applicable in continuous light cavity-type BPM visibility Detection Techniques and light-pulse generator cavity-type BPM visibility Detection Techniques, its specifically:
Embodiment one
As shown in Figure 5, this device comprises the light source 1 set gradually, and imports optical fiber 2, first coupling mechanism 9, special optical fiber 10, second coupling mechanism 11, photodetector 5 and data processing unit 6; During work: the light pulse that light source 1 sends enters a fiber arm of the first coupling mechanism 9 of high splitting ratio through importing optical fiber 2, speed up and enter special optical fiber 10.The Main Function of special optical fiber 10 is contacted with the testing sample in external environment by light wave, and then allow light-wave energy by absorption of sample.What special optical fiber 10 adopted is photonic crystal fiber of the prior art or D-type optical fiber etc.The light wave overwhelming majority after special optical fiber 10 enters a fiber arm of the second coupling mechanism 11 and has this fiber arm to export to the first coupling mechanism 9, remaining sub-fraction energy is exported by an other fiber arm of the second coupling mechanism 11, is received by photodetector 5.Circulate and so forth.First coupling mechanism 9, special optical fiber 10, second coupling mechanism 11, a composition fiber resonance cavity.By the signal that photodetector 5 detects, the visibility value of air to be measured can be obtained through data processing unit 6 process.
The object of the utility model use fiber resonance cavity is: at whole device in use, and the impact of the external mechanical vibrations be subject to is less, ensure that the precision of measurement.
Embodiment two
As shown in Figure 6, this device comprise set gradually light source 1, acousto-optic modulator 12, import optical fiber 2, import collimating apparatus 7, optical resonator 3, deriving collimating apparatus 8, deriving optical fiber 4, photodetector 5 and for carrying out light loss data to calculate the data processing unit 6 being detected sample visibility value.
Specific works principle is:
First, continuous laser will be injected an optical resonator (optical resonator comprise chamber shell, the first catoptron be arranged in the shell of chamber, the second catoptron and piezoelectric ceramics scanner) by light source, then long by piezoelectric ceramics (PZT) scanning chamber being close to the second catoptron, some longitudinal modes in chamber and laser longitudinal module are matched, when intra-cavity energy reaches certain threshold value, rapid shutoff acousto-optic modulator, makes injected optical power vanishing.Light intensity now in optical resonator decays with e index form due to loss (mainly absorbing in transmission loss and chamber).Light signal is converted to electric signal by photodetector, and is transferred to data processing unit and carries out computing, finally waits until the visibility numerical value of tested sample.
Claims (5)
1. based on an atmospheric visibility pick-up unit for cavity attenuation and vibration technique, it is characterized in that: comprise the light source, resonator cavity, photodetector and the data processing unit for carrying out light loss data to calculate the visibility value be detected in environment that set gradually.
2. the visibility pick-up unit based on cavity attenuation and vibration technique according to claim 1, is characterized in that: described pick-up unit also comprises the importing optical fiber be arranged between light source resonant cavity and the derivation optical fiber be arranged between resonator cavity and optical detector.
3. the visibility pick-up unit based on cavity attenuation and vibration technique according to claim 2, is characterized in that: described resonator cavity is optical resonator; Importing collimating apparatus is provided with between described importing optical fiber and optical resonator; Derivation collimating apparatus is provided with between described optical resonator and derivation optical fiber.
4. the visibility pick-up unit based on cavity attenuation and vibration technique according to claim 1, is characterized in that: described resonator cavity is fiber resonance cavity; Described fiber resonance cavity comprises the first coupling mechanism, special optical fiber and the second coupling mechanism; Input end and the importing Fiber connection of described first coupling mechanism, the output terminal of the first coupling mechanism is connected with the input end of special optical fiber; The output terminal of described special optical fiber is connected with the input end of the second coupling mechanism; The output terminal of described second coupling mechanism is connected with optical detector respectively at the input end of the first coupling mechanism; Described special optical fiber is for making light wave contact with the sample to be tested in external environment and absorbing; Described special optical fiber is photonic crystal fiber or D-type optical fiber.
5. the visibility pick-up unit based on cavity attenuation and vibration technique according to the arbitrary claim of claim 3, is characterized in that: described importing optical fiber and derivation optical fiber all adopt single-mode fiber.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104062236A (en) * | 2014-06-24 | 2014-09-24 | 中国科学院西安光学精密机械研究所 | Atmospheric visibility detection device based on cavity ring-down technology and application method |
| CN110672554A (en) * | 2019-11-11 | 2020-01-10 | 北京航空航天大学 | System and method for measuring concentration of calibration-free gas in random vibration driving ring-down cavity |
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- 2014-06-24 CN CN201420342967.3U patent/CN204086122U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104062236A (en) * | 2014-06-24 | 2014-09-24 | 中国科学院西安光学精密机械研究所 | Atmospheric visibility detection device based on cavity ring-down technology and application method |
| CN110672554A (en) * | 2019-11-11 | 2020-01-10 | 北京航空航天大学 | System and method for measuring concentration of calibration-free gas in random vibration driving ring-down cavity |
| CN110672554B (en) * | 2019-11-11 | 2020-09-25 | 北京航空航天大学 | Random vibration drive ring-down cavity calibration-free gas concentration measurement system |
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