CN112782126B - Remote measurement type calibration-free fire early-stage characteristic gas detection device and online demodulation method - Google Patents
Remote measurement type calibration-free fire early-stage characteristic gas detection device and online demodulation method Download PDFInfo
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Abstract
A remote measurement type calibration-free fire early feature gas detection device and an online demodulation method thereof belong to the technical field of fire detection, solve the problems that the space detection range of the existing suction type fire early gas detection device is small and the traditional remote measurement type fire early gas detection needs to be calibrated regularly, adopt a laser scattering echo signal to detect in a remote measurement mode, improve the space measurement range of the detection device, and in addition, compared with the mode of adopting an angle reflector, the remote measurement is carried out in a scattering echo signal mode, the device is simple, has better maneuverability and flexibility, and demodulates the gas concentration in real time and online by a method of directly inserting a reference air chamber filled with gas to be measured with standard concentration in the device, solves the problem that the instrument needs to be calibrated regularly, adopts a first harmonic wave to demodulate the gas concentration on a second harmonic wave normalization signal, and eliminates the influence of laser intensity, response of a photoelectric detector and change of a target reflection coefficient on a measurement result.
Description
Technical Field
The invention belongs to the technical field of fire detection, and relates to a remote measurement type calibration-free fire early-stage characteristic gas detection device and an online demodulation method thereof.
Background
At present, in the field of fire early warning detection, a widely applied fire detector is a typical point smoke fire detector, and due to an optical labyrinth structure, the fire detector is easy to miss and report, has low detection sensitivity, low precision, slow response and small detection range, and in addition, the detector needs that fire smoke forms ceiling jet flow to carry out contact detection alarm, and the ceiling jet flow which cannot form the fire smoke in a large space reaches the smoke fire detector due to a thermal barrier effect.
The development trend of the future fire detector is to realize early warning, so that the research and development of the early fire warning technology has great significance, and the main guiding idea of early fire warning is as follows: firstly, an advanced technology is adopted to improve the detection sensitivity, and detection and alarm can be carried out when fewer products are generated in the early stage of fire disaster; and secondly, detecting the products, such as early fire characteristic gases, generated in the fire process when the fire is not formed. The application space of the early fire alarm technology is quite large, and the technology is researched and developed, so that the progress and development of the novel early fire detection technology are facilitated.
The gas detection method is adopted to detect various characteristic trace gases (CO, CO2 and HCN) discharged in early stage of fire, so that early warning effect of fire can be achieved. In the prior art, the application number is CN201610908348.X, the Chinese utility model patent application with publication date of 2017, 3, 22 days, the multi-gas parallel trace detection fire early warning device and method, the application number is CN201010214367.5, the Chinese utility model patent application with publication date of 2010, 11, 24 days, the three-component fire gas detector, the application number is CN201720136860. X, the Chinese utility model patent with publication date of 2017, 11, 3 days, the extremely early inspiration type gas fire detector, the application number is CN201620217990.9, the Chinese utility model patent with publication date of 2017, 11, 3 days, the centralized fire characteristic gas detection device, the application number is CN201710765198.6, the Chinese utility model patent application with publication date of 2017, 11, 07 days, the intelligent centralized inspiration type cable fire extremely early warning device and method are all measured by pumping, the traditional inspiration type gas fire detection device is a point type contact measurement, a measurement system exists, the space measurement range is small, and response is easy.
The conventional gas detection technology such as a semiconductor gas detector, an electrochemical gas sensor, a contact gas sensor and the like has the inherent defects of low detection sensitivity, low precision, slow response, poor stability, need of periodic calibration and the like, and is difficult to meet the requirements of rapid and high-precision monitoring on trace gas discharged from early stage of fire in early warning of the fire.
The remote measurement type fire gas detection has the advantages of large space detection range, non-contact measurement, difficult report missing, quick response and obvious advantages in the early detection field of fire. For example, the Chinese patent application number CN201721298862.2 and publication date 2017, 11 and 3, namely a fire early warning system based on laser remote sensing measurement, has the characteristics of high sensitivity, good reliability and strong anti-interference capability, but the technical scheme of the utility model has the advantages of compact overall structure, short space detection distance, only 10m, no requirement for fire detection of tall space buildings (more than 12 m), long-time measurement, periodic calibration and the like, and cannot meet the practical application requirement for fire early warning.
Disclosure of Invention
The invention aims to design a remote measurement type calibration-free fire early-stage characteristic gas detection device and a remote measurement type calibration-free fire early-stage characteristic gas detection method, so as to solve the problems that the space detection range of the existing air suction type fire early-stage gas detection device is small and the traditional remote measurement type fire early-stage gas detection needs to be calibrated regularly.
The invention solves the technical problems through the following technical scheme:
A telemetry calibration-free fire early feature gas detection device comprising: the device comprises a collimation focusing transceiving integrated optical component (1), an ARM embedded acquisition control analysis module (2), a DFB laser (3), a reference air chamber (5) and a single-mode optical fiber (6); two output ends of the ARM embedded acquisition control analysis module (2) are respectively connected with the collimation focusing transceiving integrated optical component (1) and the DFB laser (3); one end of the single-mode optical fiber (6) is connected with the collimation focusing receiving and transmitting integrated optical component (1), and the other end of the single-mode optical fiber is connected with the output end of the reference air chamber (5); the input end of the reference air chamber (5) is connected with the output end of the DFB laser (3), the laser receiving device (3) emits detection light for detection in a telemetry mode, the collimation focusing receiving and transmitting integrated optical component (1) collimates laser detection signals emitted by the DFB laser (3) and receives laser scattering echo signal light, and the reference air chamber (5) is filled with characteristic gas with standard concentration and is used for carrying out on-line calibration on the concentration of the characteristic gas to be measured, which is measured in real time.
Light emitted by the DFB laser (3) enters the reference air chamber (5), then laser enters the collimation focusing receiving and transmitting integrated optical component (1) through the single-mode optical fiber (6), and then the collimation focusing receiving and transmitting integrated optical component (1) emits detection light which is approximately parallel to light outwards, the detection light is transmitted in a space optical path, smoke generated by fire is reflected by a wall body or ground and other reflectors to form echo signal light, the echo signal light is recycled through the smoke again through the collimation focusing receiving and transmitting integrated optical component (1), and the echo signal light is sent to the ARM embedded acquisition control analysis module (2) for calculation processing, laser scattering echo signals are adopted for detection in a telemetry mode, so that the space measurement range of a detection device is improved.
As a further improvement of the technical scheme of the present invention, the collimating focusing transceiving integrated optical component (1) comprises: a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end of the interior of the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) in the interior of the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode fiber (6) is connected with the input end of the detection light collimator (11).
As a further improvement of the technical scheme of the invention, the detection light collimator (11) comprises a detection light collimating lens (111) and an optical fiber interface (112), the detection light collimating lens (111) and the optical fiber interface (112) are coaxially arranged, and one end of the single-mode fiber (6) is connected in the optical fiber interface (112).
As a further improvement of the technical scheme of the present invention, the reference air chamber (5) includes: the single-mode fiber laser comprises two GRIN collimating lenses (51) and a reference air chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference air chamber body (52), the input end of the reference air chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference air chamber body (52) is connected with one end of the single-mode fiber (6).
As a further improvement of the technical scheme of the invention, the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degree.
The remote measuring type calibration-free fire early-stage characteristic gas detection device comprises an ARM embedded acquisition control analysis module (2) which sends out a driving signal to drive detection laser sent out by a DFB laser (3), wherein the DFB laser (3) enters a reference air chamber (5), and after being collimated by a collimation focusing transceiving integrated optical component (1), the device emits, detects and receives scattered echo signal light, and then the ARM embedded acquisition control analysis module (2) adopts the following formula to demodulate the concentration of characteristic gas to be detected in real time on line:
In the formula, xL represents the integral concentration of the characteristic gas to be measured in the open measuring light path,
X refLref represents the integral concentration of the characteristic gas of standard concentration in the reference gas chamber (5), and S 2f/S1f represents the first harmonic to second harmonic normalization signal of the characteristic gas to be measured; s 2f/S1fref represents the first harmonic versus second harmonic normalized signal for a standard concentration of the characteristic gas.
The method eliminates the influence of laser light intensity, response of a photoelectric detector and target reflection coefficient change on a measurement result, and the method directly inserts a reference air chamber filled with gas to be measured with standard concentration into the device to demodulate the gas concentration in real time and on line, thereby solving the problem that the instrument needs to be calibrated regularly and really realizing long-term calibration-free instrument.
As a further improvement of the technical scheme of the present invention, the collimating focusing transceiver integrated optical component (1) includes: a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end of the interior of the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) in the interior of the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode fiber (6) is connected with the input end of the detection light collimator (11).
As a further improvement of the technical scheme of the invention, the detection light collimator (11) comprises a detection light collimating lens (111) and an optical fiber interface (112), the detection light collimating lens (111) and the optical fiber interface (112) are coaxially arranged, and one end of the single-mode fiber (6) is connected in the optical fiber interface (112).
As a further improvement of the technical scheme of the present invention, the reference air chamber (5) includes: the single-mode fiber laser comprises two GRIN collimating lenses (51) and a reference air chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference air chamber body (52), the input end of the reference air chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference air chamber body (52) is connected with one end of the single-mode fiber (6).
As a further improvement of the technical scheme of the invention, the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degree.
The invention has the advantages that:
(1) According to the technical scheme, the DFB laser (3) emits light to enter the reference air chamber (5), then the laser enters the collimation focusing transceiving integrated optical component (1) through the single-mode optical fiber (6), the collimation focusing transceiving integrated optical component (1) emits detection light of approximately parallel light outwards, the detection light is transmitted in a space optical path, smoke generated by fire is transmitted, and echo signal light is formed after being reflected by reflectors such as walls or floors and the like, the echo signal light is recycled through the smoke again through the collimation focusing transceiving integrated optical component (1) and is sent to the ARM embedded acquisition control analysis module (2) for calculation processing, laser scattering echo signals are adopted for detection in a telemetry mode, the space measurement range of a detection device is improved, in addition, compared with the method of adopting an angle reflector mode for telemetry in a scattering echo signal mode, the device is simple, and better maneuverability and flexibility are achieved.
(2) The method eliminates the influence of laser light intensity, response of a photoelectric detector and target reflection coefficient change on a measurement result, and the method directly inserts a reference air chamber filled with gas to be measured with standard concentration into the device to demodulate the gas concentration in real time and on line, thereby solving the problem that the instrument needs to be calibrated regularly and really realizing long-term calibration-free instrument.
(3) According to the technical scheme, the collimation optical axis of the collimation focusing receiving and transmitting integrated optical component (1) is strictly parallel to the receiving optical axis, so that scattered light signals scattered back by diffuse reflection background are effectively received by the photoelectric detector (13).
(4) According to the technical scheme, the surface of the signal light receiving lens (12) is plated with the band-pass film with the wave band of 1500-1600nm, so that the signal light transmittance is further improved, the signal to noise ratio is further improved, in addition, light with other wave bands can be filtered out and enter the photoelectric detector, and the photoelectric detector is prevented from being saturated.
Drawings
FIG. 1 is a working block diagram of a telemetry calibration-free fire early feature gas detection device according to an embodiment of the present invention;
fig. 2 is a top view of a collimating, focusing, transceiving integrated optical component according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The technical scheme of the invention is further described below with reference to the attached drawings and specific embodiments:
As shown in fig. 1, a fire early multi-gas laser telemetry device includes: the device comprises a collimation focusing transceiving integrated optical component 1, an ARM embedded acquisition control analysis module 2, a DFB laser 3, a reference air chamber 5 and a single-mode optical fiber 6; the two output ends of the ARM embedded acquisition control analysis module 2 are respectively connected with the input ends of the collimation focusing transceiving integrated optical component 1 and the DFB laser 3; one end of the single-mode fiber 6 is connected with the collimation, focusing and transceiving integrated optical component 1, and the other end is connected with the output end of the reference air chamber 5; the input end of the reference air chamber 5 is connected with the output end of the DFB laser 3.
As shown in fig. 2, the collimating, focusing, transceiving integrated optical component 1 includes: a detection light collimator 11, a signal light receiving lens 12, a photodetector 13, an indication laser 14, a cylindrical housing 15; the detection light collimator 11 is arranged outside the cylindrical shell 15, and the optical axis (collimation optical axis) of the detection light collimator 11 and the optical axis (receiving optical axis) of the signal light receiving lens 12 are designed in an off-axis mode, namely, the collimation optical axis and the receiving optical axis are parallel but not coincident, so that the design mode has a simple structure, and is stable and reliable; the signal light receiving lens 12 is arranged at one end of the interior of the cylindrical shell 15, the photoelectric detector 13 and the signal light receiving lens 12 are coaxially arranged on a receiving optical axis, the photoelectric detector 13 is arranged at the focus of the signal light receiving lens 12 in the interior of the cylindrical shell 15, and the electric signal input end of the photoelectric detector 13 is connected with the ARM embedded acquisition control analysis module 2; the indicating laser 14 is arranged at the top of the cylindrical shell 15, and the light emitted by the indicating laser 14 is in a visible light wave band (red or green laser) and is parallel to the light emitted by the detecting light collimator 11, so as to indicate the emitting direction of the light beam; one end of the single-mode fiber 6 is connected to the input end of the detection light collimator 11.
When the remote sensing detection is carried out on the fire early-stage characteristic gas based on the open light path, the design of the light path part can cause important influence on the overall detection performance, the collimation effect of the DFB laser 3 directly influences the detection distance and the intensity of the echo signal, and the parallelism of the collimation light path and the optical axis of the receiving light path can also directly influence the intensity of the echo signal detected by the system. The collimation optical axis of the collimation focusing receiving and transmitting integrated optical component 1 designed by the technical scheme is strictly parallel to the receiving optical axis, so that the scattered light signal scattered back by the diffuse reflection background is effectively received by the photoelectric detector 13.
The model of the main control chip of the ARM embedded acquisition control analysis module is STM32F407ZGT6, and the ARM embedded acquisition control analysis module is used for: 1) Generating a low frequency sawtooth signal (10 Hz) and a high frequency sine wave signal (10 KHz) for modulation of the DFB laser 3; 2) The temperature of the DFB laser 3 is precisely controlled by a PID algorithm, and the temperature control precision is +/-0.01 ℃; 3) The signal received by the photodetector 13 is processed such as collection, amplification and filtering, a second harmonic signal (2 f) and a first harmonic signal (1 f) are demodulated, the gas concentration is demodulated according to an embedded demodulation algorithm, the obtained gas concentration is displayed in real time, and data is uploaded through RS-485, and in addition, the module also has the functions of gas concentration overrun audible and visual alarm and the like.
As shown in fig. 2, the probe light collimator 11 includes a probe light collimating lens 111 and an optical fiber interface 112, the probe light collimating lens 111 and the optical fiber interface 112 are coaxially disposed, one end of the single-mode fiber 6 is connected to the optical fiber interface 112, and the distance from the end surface of the single-mode fiber 6 to the probe light collimating lens 111 can be finely adjusted.
The signal light receiving lens 12 and the detecting light collimating lens 111 both adopt an aspherical mirror, and compared with a spherical mirror, the structure is simple by adopting an aspherical mirror design mode, the collimating and focusing effects are better, and the lens materials are all made of calcium fluoride materials (CaF 2), and the light transmittance of the materials in the near infrared-middle infrared band can reach more than 90%. The surface of the signal light receiving lens 12 is plated with a band-pass film with 1500-1600nm wave band, so that the signal light transmittance is further improved, the signal to noise ratio is further improved, and in addition, light with other wave bands can be filtered out to enter the photoelectric detector, so that the photoelectric detector is prevented from being saturated.
The reference air chamber 5 includes: the optical fiber laser comprises two GRIN (fiber gradient refractive index) collimating lenses 51 and a reference air chamber body 52, wherein the two GRIN collimating lenses 51 are respectively arranged at the input end and the output end of the reference air chamber body 52, the input end of the reference air chamber body 52 is connected with the output end of the DFB laser 3, and the output end of the reference air chamber body 52 is connected with one end of the single-mode optical fiber 6. The spacing between the two GRIN collimating lenses 51 is 5cm, and in order to avoid etalon noise caused by internal reflection at the end faces of the two GRIN collimating lenses 51 in the optical path, a small angle of about 0.3 ° is maintained between the end faces of the two GRIN collimating lenses 51.
The calibration-free gas concentration demodulation method by adopting the device comprises the following steps:
taking fire characteristic trace gas CO demodulation as an example, when the sinusoidal modulation frequency ω=2pi f of the current injected into the DFB laser 3 by the ARM embedded acquisition control analysis module 2, the instantaneous frequency v (t) of the emitted laser light of the DFB laser 3 is:
Wherein, The laser center frequency is the frequency modulation amplitude, a is the frequency modulation amplitude, and t is the time.
Considering the intensity modulation effect of current on laser light, since the nonlinear modulation amplitude is very small, the output intensity I 0 (t) of the laser can be regarded as linear modulation, expressed as:
Wherein, For laser at central frequency/>The average intensity at i 1 is the linear intensity modulation (from/>Normalized), ψ 1 is the linear modulation phase shift.
When laser passes through the trace gas CO with the measured characteristic, the light intensity attenuation accords with the lambert-beer law, and under the condition of small absorbance, a (upsilon) L is less than 0.05, and the expression of the transmitted light intensity I t can be simplified as:
wherein a (v) (cm -1) is the absorption coefficient of the gas, L (cm) is the optical path length, aL is the absorbance, η is the reflectance of the actual target, P (atm) is the gas pressure, x CO is the concentration of CO gas (mole fraction or volume fraction, commonly used volume fraction units are ppm), S CO(atm-1·cm-2) and The absorption line intensity and the line type function, respectively.
The gas absorption coefficient a (v) (cm -1) in the formula (3) is a function of the instantaneous laser frequency v (t), and is obtained by performing fourier series expansion on the function:
Wherein, Is the k-th order fourier expansion coefficient of the absorption coefficient.
The k-th harmonic component of equation (4) can be expressed as:
From equation (5), it can be seen that the magnitudes of the Fourier coefficients of each order of the absorption coefficient a (v) are proportional to the product of the concentration of the gas and the optical path length.
An important problem in the remote control of fire early feature gases based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) is the need to use natural environments (such as natural objects like buildings, walls, floors or trees) as targets, where the actual reflectivity of the targets is unknown. To eliminate the effect of this factor on the measurement, one widely used method is a wavelength modulation technique, and uses the first harmonic to normalize the second harmonic signal, known as the "2f/1f" method. The phase-locked amplifier can be used to separate the modulated frequency subharmonic signals from the detector output original signals. In order to reduce the effect of the phase difference between the original signal and the reference signal on the amplitude measurement, the original signal is demodulated simultaneously using cos (kωt) and sin (kωt), resulting in the X and Y components of the k-th harmonic, respectively.
The amplitude of the second harmonic (S 2f) signal can be expressed as:
Wherein G is the response coefficient of the photodetector. Since the characteristic absorption peak of the gas is a symmetrical structure, the odd-order fourier coefficient is 0 at the center frequency of the absorption peak. Thus the formula (6) can be further simplified to:
for trace gas concentrations, there is 1> > H k (k=0, 1,2·.) and the amplitude of the first harmonic signal (S 1f) can be found in the same way as:
Normalizing the second harmonic signal (S 2f) with the first harmonic signal (S 1f) yields:
As can be seen from the formula (9), the S 2f/S1f signal is not related to the light intensity, the response G of the photodetector and the reflection system eta of the target, so that the influence of the light intensity, the response of the photodetector and the change of the reflection coefficient of the target on the measurement result can be eliminated by adopting the S 2f/S1f signal to demodulate the gas concentration. This feature is of great importance in open optical path for gas telemetry applications.
There is also a very important practical problem in using the S 2f/S1f signal to demodulate the gas concentration, namely how to implement the calibration of the instrument. The traditional method is to put a series of gases to be measured filled with different standard concentrations into a measuring light path, measure S 2f/S1f signals corresponding to the different standard concentrations, and further obtain an instrument calibration curve under the measuring condition. The method is time-consuming and labor-consuming, and with the use of the instrument, the problem of inaccurate measurement exists, the calibration needs to be carried out regularly, and in addition, the actual use environment of the instrument is different from the laboratory calibration environment, and measurement errors can be introduced.
To overcome this problem, a reference cell of length L ref is inserted directly between the DFB laser and the detection collimator of the device, the reference cell being filled with a standard concentration gas, as shown in FIG. 1. Assuming that the concentration of the standard CO gas in the reference gas chamber is x ref, the measured S 2f/S1f signal is:
Where x refLref is the integrated concentration of standard CO gas in the reference gas cell, x CO L is the integrated concentration of the measured CO gas in the open measurement light path, and a can be regarded as a constant.
When the instrument is calibrated, only the laser beam emitted from the collimator is directly reflected to the photoelectric detector by the target, and a reference measurement signal is obtained firstly, namely:
S2f/S1f,ref＝AxrefLref (11)
from equation (10) and equation (11):
For example, when the reference gas chamber is filled with CO standard gas having a concentration of 10000ppm, the integrated concentration of CO in the reference gas chamber is 500 ppm.m, and the integrated concentration of CO measured in the open optical path is:
The method of directly inserting the reference air chamber into the device solves the problem that the instrument needs to be calibrated regularly, truly realizes long-term calibration-free of the instrument, and has the advantages of no influence of measurement environment, high measurement precision, high sensitivity, no need of additionally adding a reference light path, simple structure and the like.
The calibration-free design scheme of the device comprises the following steps: the calibration-free design scheme of the device is that a reference air chamber with the length of L ref is directly inserted between a DFB laser and a detection light collimator of the device, the reference air chamber is filled with standard concentration gas to be detected (10000 ppm CO or 10000ppm CO2 or 10000ppm HCN), the reference air chamber is composed of a pair of optical fiber Gradient Refractive Index (GRIN) collimating lenses sealed in the air chamber, and the distance between the two collimating lenses is 5cm. To avoid etalon noise caused by internal reflection at the end faces of the two GRIN lenses in the optical path, a small angle of cant (about 0.3 °) is maintained between the end faces of the two GRIN lenses.
The calibration-free gas concentration demodulation method comprises the following steps: the method adopts a method of normalizing signals (S 2f/S1f) of first harmonic and second harmonic to demodulate the gas concentration, eliminates the influence of the laser intensity, the response of a photoelectric detector and the change of a target reflection coefficient on a measurement result, and simultaneously, directly inserts a reference gas chamber filled with gas to be measured with standard concentration into the device, thereby obtaining the gas concentration by the formulaThe method has the advantages of no influence of measuring environment, high measuring precision, high sensitivity, no need of additionally adding a reference light path, simple structure and the like.
The DFB laser 3 enters the reference air chamber 5, the reference air chamber 5 is filled with standard concentration gas to be detected (10000 ppm CO or 10000ppm CO2 or 10000ppm HCN), then laser enters the detection light collimator 11 through the single-mode optical fiber 6, the detection light is transmitted in a space light path, smoke generated by fire disaster is transmitted through the detection light collimator 11, echo signal light is formed after being reflected by reflectors such as a wall body or the ground, the echo signal light passes through the smoke again and is collected by the signal light receiving lens 12 and focused on the photoelectric detector 13, a band-pass film with 1500-1600nm wave band is plated on the surface of the signal light receiving lens 12 for filtering the influence of ambient stray light on the detection device, compared with the method adopting a band-pass filter, the method has the advantages of being more stable and compact in structure without introducing a filter component. In addition, the device adopts the reference air chamber 5 filled with the gas to be measured with standard concentration to conduct online demodulation on the gas concentration measured in real time, long-term calibration-free of the device is achieved, and the accuracy and reliability of system measurement are improved.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. Remote measurement type calibration-free fire early characteristic gas detection device is characterized by comprising: the device comprises a collimation focusing transceiving integrated optical component (1), an ARM embedded acquisition control analysis module (2), a DFB laser (3), a reference air chamber (5) and a single-mode optical fiber (6); two output ends of the ARM embedded acquisition control analysis module (2) are respectively connected with the collimation focusing transceiving integrated optical component (1) and the DFB laser (3); one end of the single-mode optical fiber (6) is connected with the collimation focusing receiving and transmitting integrated optical component (1), and the other end of the single-mode optical fiber is connected with the output end of the reference air chamber (5); the input end of the reference air chamber (5) is connected with the output end of the DFB laser (3), the DFB laser (3) emits detection light for detection in a telemetry mode, the collimation focusing and transceiving integrated optical component (1) collimates laser detection signals emitted by the DFB laser (3) and receives laser scattering echo signal light, and the reference air chamber (5) is filled with characteristic gas with standard concentration and is used for carrying out online calibration on the concentration of the characteristic gas to be measured, which is measured in real time;
The collimation focusing receiving and transmitting integrated optical component (1) comprises: a detection light collimator (11), a signal light receiving lens (12), a photoelectric detector (13), an indication laser (14) and a cylindrical shell (15); the detection light collimator (11) is arranged outside the cylindrical shell (15), and the optical axis of the detection light collimator (11) and the optical axis of the signal light receiving lens (12) are designed in an off-axis mode; the signal light receiving lens (12) is arranged at one end of the interior of the cylindrical shell (15), the photoelectric detector (13) and the signal light receiving lens (12) are coaxially arranged, the photoelectric detector (13) is arranged at the focus of the signal light receiving lens (12) in the interior of the cylindrical shell (15), and the electric signal input end of the photoelectric detector (13) is connected with the ARM embedded acquisition control analysis module (2); the indicating laser (14) is arranged at the top of the cylindrical shell (15); one end of the single-mode fiber (6) is connected with the input end of the detection light collimator (11);
The reference air chamber (5) comprises: the single-mode fiber laser comprises two GRIN collimating lenses (51) and a reference air chamber body (52), wherein the two GRIN collimating lenses (51) are respectively arranged at the input end and the output end of the reference air chamber body (52), the input end of the reference air chamber body (52) is connected with the output end of the DFB laser (3), and the output end of the reference air chamber body (52) is connected with one end of the single-mode fiber (6).
2. The remote measurement type calibration-free fire early characteristic gas detection device according to claim 1, wherein the detection light collimator (11) comprises a detection light collimating lens (111) and an optical fiber interface (112), the detection light collimating lens (111) and the optical fiber interface (112) are coaxially arranged, and one end of the single-mode fiber (6) is connected in the optical fiber interface (112).
3. The remote calibration-free fire early feature gas detection device according to claim 1, wherein the distance between the two GRIN collimating lenses (51) is 5cm, and the included angle between the end faces of the two GRIN collimating lenses (51) is 0.3 degrees.
4. An on-line demodulation method applied to a remote measurement type calibration-free fire early-stage characteristic gas detection device as claimed in any one of claims 1 to 3 is characterized in that an ARM embedded acquisition control analysis module (2) sends out a driving signal to drive detection laser sent out by a DFB laser (3), the DFB laser (3) enters a reference air chamber (5), and after being collimated by a collimation focusing and transceiving integrated optical component (1), echo signal light which is detected and scattered is received is emitted, and then the concentration of characteristic gas to be detected is demodulated on line in real time by the ARM embedded acquisition control analysis module (2) by adopting the following formula:
In the formula, xL represents the integral concentration of the characteristic gas to be measured in the open measuring light path, Integral concentration of characteristic gas representing standard concentration in reference gas chamber (5)/>A first harmonic to second harmonic normalization signal representing the characteristic gas to be measured; /(I)The first harmonic versus second harmonic normalized signal representing the standard concentration of the characteristic gas.
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