CN100447555C - Laser signal real-time continuous extraction method for atmospheric suspended particulate matters - Google Patents
Laser signal real-time continuous extraction method for atmospheric suspended particulate matters Download PDFInfo
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Abstract
The invention discloses a real-time continuous extraction method of laser signals of atmospheric particle suspended matters, which adopts a red semiconductor diode laser with the wavelength range of 650-675 nm as a scattering light source of aerosol particles, and forms horizontal flat-long light spots on a focal plane through a collimating lens and an optical rotator through a cylindrical lens A and a cylindrical lens B after the adjustment of a collimating lens and an optical rotator, and places yttrium vanadate crystals behind the cylindrical lens B to obtain two beams of o light and e light with equal energy, and two narrow strip-shaped light spots are formed in a laser detection area; the atmospheric aerosol particles pass through the two light spots one by one; laser is scattered by aerosol particles, scattered light is collected by a half ellipsoidal mirror, two strong scattering peaks are obtained, and signals collected by the avalanche photodiode are transmitted to an electrical system. The invention is used for accurately measuring the distribution of particles with aerodynamic diameters of 0.5 to 10 microns and the content of particles with biological characteristics.
Description
Technical field
The present invention relates to field of photoelectric technology, be specifically related to a kind of signal acquisition method of atmosphere suspended particulate substance.
Background technology
In the place that environment is polluted, what suck when people breathe is not pure air but gasoloid, and it has material impact to people's life and health.Atmospheric aerosol (Aerosols) is meant solid or the liquid particles that is suspended in the atmosphere, usual some seen phenomenons, as: dust, fumigation, cigarette, mist, haze etc. all belong to aerocolloidal category.Gasoloid mainly depends on its composition, concentration, source and particle diameter to the harm intensity of human body.The scope of aerosol particle size from 0.001 to the 100 μ m.The character of different size aerosol particle often difference is very big, for example the floating life-span of the coarse particle that diameter is bigger in atmosphere is very short, be about several hrs, the less fine grained life-span of diameter then can reach a couple of days, and the energy drift is to thousands of kilometers places in addition. the particle composition is main virulence factor, and which kind of disease whether decision be harmful to and cause.Generally speaking, particle diameter is greater than 30 μ m, particle, the possibility that enters lower respiratory tract is very little, 10-30 μ m, the particle overwhelming majority be deposited on nasal cavity, 5-10 μ m, particle can enter trachea and bronchus, only less than 5 μ m, particle PM5 just can enter into deep respiratory tract and interspersing among on the alveolar.Obviously, only less than 10 μ m, the particle gasoloid be only the most dangerous.
To the aerosol sampling apparatus of particle measurement, be a kind of multistage knocker in the prior art.This instrument mainly separates collection based on the inertia impact principle to particle, can obtain the particle of different-grain diameter scope on different collection levels.An important parameter of multistage knocker is exactly a cut-off diameter at different levels, and it has determined collectable granulometric range in each level.In the ideal case, when gasoloid passes through each grade, can think and have only diameter could pass through that other particle all will be collected less than the particle of this grade cut-off diameter; Because multistage knocker cut-off diameter at different levels successively decreases from top to bottom, so collected granulometric range is located between the cut-off diameter of this grade cut-off diameter and upper level in each grade.
Adopt this method to be unfavorable for very much continuous data sampling, because the gas mass flow of multistage knocker cut-off diameters at different levels during with work is relevant, so the vacuum pump of different pumping speed, its experimental result is all inequality.The later stage measurement data will be very inaccurate, and will be thinless between its detection zone, and measurement result can not be monitored sight in real time simultaneously.
Summary of the invention
The object of the invention provides a kind of laser signal real-time continuous extracting method of atmosphere suspended particulate substance, the signal that extracts after treatment can be continuous, real-time, online, detect, show the aerodynamic diameter of atmospheric sample particulate, the population of various particle diameters simultaneously.
Technology implementation scheme of the present invention is:
The laser signal real-time continuous extracting method of airborne particulate suspension comprises:
(1), adopt wavelength coverage at the red semiconductor diode laser of 650～675nm scattering light source as particulate, laser normal incidence behind the collimation lens collimation is to polarization apparatus, by the polarization direction of polarization apparatus adjusting shoot laser, to satisfy of the requirement of vanadic acid yttrium birefringece crystal to the polarization direction; The directional light that expands after restrainting is constant at the vertical direction hot spot behind cylindrical lens A, horizontal direction will be pressed narrow, cylindrical lens B horizontal positioned subsequently, the beam level direction is constant, and vertical direction is pressed narrow, cylindrical lens B is placed in the focus of cylindrical lens A, become the hot spot of the prolate of level on the focal plane, the vertical direction hot spot is Gaussian distribution, and the distance that changes between cylindrical lens A, the B can change in focal plane hot spot horizontal size, regulate the position of cylindrical lens, can change the size and the position thereof of hot spot; Place yttrium vanadate crystal behind the cylindrical lens B, utilize the polarization characteristic of yttrium vanadate crystal, regulate the polarization direction of incident laser, can obtain o light and e light that two beam energies equate, form the hot spot of two fillet shapes in the laser acquisition district;
(2), atmospheric aerosol particle is one by one successively by these two hot spots;
(3), laser is through the particulate scattering, scattered light is collected by half ellipsoidal mirror, and obtains two strong scattering peaks, avalanche photodide is collected the scattered light that scatters from ellipsoidal mirror, the signal that avalanche photodide is collected is sent to electricity system;
(4), light trap is used for absorbing red laser, the elimination optical noise;
Detecting area and optical channel and detector are isolated and sealing with window, avoid extraneous spuious thing to enter detecting area and influence signal.
Described extracting method is characterized in that the diode laser output power is not less than 28mW, and power fluctuation behind the collimation lens collimation, obtains beam divergence angle less than 5 milliradians less than ± 2%, and spot size is approximately
The angle of divergence is the output laser of 2mrad.
Described extracting method is characterized in that detecting area forms the hot spot of two fillet shapes in the laser acquisition district, and spot size is about 1.2 * 0.12mm
2, two hot spots are about 0.1mm in focus place center distance.
Described extracting method is characterized in that the bore of ellipsoidal mirror is about
Described extracting method, it is characterized in that atmospheric aerosol particle is to realize by the following method by these two hot spots successively one by one: a sample channel is set, sample channel is made up of inside and outside two-layer two coaxial pipelines, the inner and outer pipes outlet all has a tapered openings, vertical interval 0.75mm, interior pipe passes through sample flow, flow by shell between the inner and outer pipe, shell stream is the clean gas through filtering, sample flow is a detected sample gas, the flow of keeping shell stream and sample flow be than constant, and shell stream and sample flow are respectively by pumping gas.
Described extracting method, it is characterized in that total flow keeps the constant rate of 5 ± 0.1L/min, keep the shell flow at 5 ± 0.1L/min, the sample flow is at 1 ± 0.2L/min, the pressure of detecting area is lower than the about 90Torr of pressure of ambient gas, and the gas velocity in sample intake passage exit is about the hundreds of rice of per second.
Function advanced person of the present invention is adapted to carry out indoor or field operation.The content that can be used for accurately measuring the distribution of particles of 0.5 to 10 micron of aerodynamic diameter and have the biological nature particle.Can continuous, real-time, online detection and show simultaneously, the aerodynamic diameter of group suppression atmospheric aerosol particle, the grain spectrum distributes and the sum of all kinds of particles.
Description of drawings
Fig. 1 is a sample intake passage structural representation of the present invention.
Fig. 2 is a light channel structure synoptic diagram of the present invention.
Fig. 3 is a scattered light collection structure synoptic diagram of the present invention.
Fig. 4 is a sample intake passage structural drawing of the present invention.
Fig. 5 is apparatus of the present invention structural drawing.
Fig. 6 is sample flow of the present invention, shell current control electrical schematic diagram.
Fig. 7 is a pressure sensor circuit block diagram of the present invention.
Fig. 8 is vacuum pump control block diagram of the present invention.
Fig. 9 detects treatment circuit for APD of the present invention.
Figure 10 is a signal processing circuit of the present invention.
Embodiment
Referring to accompanying drawing.
The present invention relates to the content of three aspects: 1, sample introduction and flow system, draw aerosol sample, produce collimated particle stream; 2, optical measuring system forms the focal beam spot that is fit to particle diameter and measurement; 3, electrical signal processing system is handled photosignal, the air-flow control circuit.
The technical indicator of mainly finishing of the present invention: 1, measure particle size range: 0.5 ~ 10 micron.2, particle types: solid and nonvolatile liquid particle.3, maximum particle concentration: 0.5 micron: in concentration is that 1500/cm3 particle coincidence factor is less than 10%; 10.0 micron: in concentration is that 600/cm3 particle coincidence factor is less than 10%.4, flow rate: aerosol sample: 1.0 ± 0.2L/Min, shell stream: 4.0 ± 0.1L/Min, total air flow: 5.0 ± 0.1L/Min.6, flow control: by the built-in brushless direct-current pump of FEEDBACK CONTROL of total flow and shell stream.7, working temperature: 10 ~ 35 ℃.8, working relative humidity: 0 ~ 95%RH.8, LASER Light Source: diode laser (redness): 30mW, 675nm, UV LASER Light Source: 2kHz, 30 μ J/ pulses.9, fluorescence detector: avalanche photodetector (APD), 10, instrument power source: 220VAC, 50Hz, maximum 6A.
Sample introduction and air flow system:
Air enters sampling channel through the sampling of aerodynamics 10 μ m sampling cutting head.Sample is divided into two strands, and a part of sample flow (sample stream) enters the measurement that the scattered light collecting chamber carries out the flight time through interior pipe, and a part (shell stream) then flows through from outer tube through shell stream pump in addition, and two strands of gases are extracted instrument out through total stream pump again.Guaranteed that atmosphere suspended particle matter sample equates on dynamics.Shell stream partial discharge is by the control of shell stream pump, and system software carries out closed-loop control by the value that reads pressure transducer to shell stream, controls its flow velocity and keeps in balance.After the sample of sample stream leaves nozzle, just enter the scattered light collecting chamber and carry out particle movement speed and scattered light intensity measurement.All there is filtration unit the air inlet gas outlet of shell stream pump and sample stream pump, and the inlet end filtration unit is avoided polluting in order to the protection pump housing, and the outlet side filtration unit can prevent filth gas stream of pollution in the pump.Be lower than the about 90Torr of ambient pressure by software control to reach cavity air pressure, guarantee that airborne particulate enters nozzle region one by one, software control system total flow simultaneously is the constant rate of maintenance 5 ± 0.1L/min, control shell stream pump simultaneously to keep shell stream at 5 ± 0.1L/min, make sample stream be stabilized in the flow of 1 ± 0.2L/min, guarantee the accuracy of measuring.
Single particulate enters measurement zone by the nozzle accelerating region.Particle one leaves nozzle, and it is intrafascicular just to enter two red lasers that overlap of bundle.This two bundle laser and particle effect will produce a scattering bimodal signal relevant with each particle flight time.By measuring the peak-to-peak time of bimodal signal, can obtain the aerodynamic diameter of each particulate, and the bimodal intensity level of scattering also can be used to other character of particle.Scattered light is surveyed with avalanche photodide.
The upper end is the gasoloid sample channel, enters for the gas (being generally atmosphere) that contains particulate, or is connected with system such as aerosol generator.This sample channel is made up of inside and outside two-layer two coaxial pipelines, and the inner and outer pipes outlet all has a tapered openings, vertical interval 0.75mm (design will be adopted the conductive material manufacturing, to reduce the particle loss that static causes).This structure internal layer is sample flow (Sample Flow), and outside is that shell flows (Sheath Flow).The outer tube upper side is extracted by a brushless direct-current pump, through two filtrators, the particulate that carries in the air-flow is all removed, and finally forms agranular clean gas (being shell stream), sends the lower end of outer tube again back to, and two parts are isolated by 0 circle up and down.The mid-aperture of pipeline of flowing through at shell stream by the pressure reduction at its two ends of pressure sensor monitoring, and is controlled the pumping speed of shell stream pump in view of the above, to proofread and correct air pressure (between 400mbar and 1030mbar from normal moveout correction, also can manual correction).During work, the flow of keeping the shell air-flow accounts for about 80% of total flow, is generally 4L/Min, and other 20% are supplied with by the sample flow that flows in the interior conduit, are generally 1L/Min.
Scattered light collecting chamber bottom is over against the output duct at air intake opening place, be connected to filtrator (oil vapour that produces when preventing the pump running pollutes cavity and pipeline) and another brushless direct-current pump (always flowing pump) thereafter, cooperate two other pressure transducer (total pressure difference and absolute pressure), the total flow of guaranteeing system is 5L/Min, and the pressure in the maintenance test chamber is lower than the about 90Torr of pressure of ambient gas, and at this moment the gas velocity in sample introduction pipe exit is about the hundreds of rice of per second.
Absolute pressure transducer then is used for the modifying factor ambient pressure environment and changes the influence that (as change the atmospheric variation that causes because of sea level elevation) brings measurement.
Under above design conditions, when the gasoloid gas of sampling when just having entered test chamber, be and stablize acceleration mode by spout.Particulate quickens with gas molecule, and owing to the different inertia differences that possess of its quality, small-particle obtains bigger speed, and bigger particle obtains less speed.According to the particle flight used time of certain distance, just can measure its particle diameter.
The gasoloid particle diameter that obtains in quickening air-flow promptly is an aerodynamic size.Aerodynamic size information is very important, because it is directly relevant with gasoloid behavior among the human respiratory system.
Another vital role of shell air-flow is that particulate is limited to air-flow center (focussing force), surveys highly beneficial to the back particle diameter.
The grain diameter measurement district under the sampling system spout, about 0.5mm distance, too big distance can reduce detection of particles efficient, then can produce too much parasitic light in the chamber too for a short time.
Optical measuring system:
The design division of optical element is as follows:
1, laser light source
System adopts wavelength coverage at the red semiconductor diode laser of the 650～675nm scattering light source as particulate, adopt the permanent power driven with current sources of high precision constant current of design voluntarily, power stability with bonding transverse mode semiconductor diode laser, laser output power is not less than 28mW, power fluctuation is less than ± 2%, with the collimation lens collimation, beam divergence angle is less than 5 milliradians earlier for diode laser, and spot size is approximately
2, collimation lens
Selecting suitable collimation lens is 3mm to obtain spot diameter, and the angle of divergence is the output laser of 2mrad.
3, polarization apparatus
Laser normal incidence behind the collimation is to polarization apparatus, by the polarization direction of polarization apparatus adjusting shoot laser, to satisfy the requirement of calcite birefringence crystal to the polarization direction.
4, cylindrical lens A, B
The directional light that expands after restrainting is constant at the vertical direction hot spot behind cylindrical lens A, horizontal direction will be pressed narrow, cylindrical lens B horizontal positioned subsequently, the beam level direction is constant, vertical direction is pressed narrow, because cylindrical lens B is placed in the focus of cylindrical lens A, therefore on the focal plane, become the hot spot of the prolate of level, the vertical direction hot spot is Gaussian distribution, the distance that changes between cylindrical lens A, the B can change in focal plane hot spot horizontal size, regulate the position of cylindrical lens, can change the size and the position thereof of hot spot.
5, yttrium vanadate crystal
Utilize the polarization characteristic of yttrium vanadate crystal, regulate the polarization direction of incident laser, can obtain o light and e light that two beam energies equate.Select the yttrium vanadate crystal of different-thickness for use, can adjust the distance between the two-beam spot.
6, detecting area
The red semiconductor diode laser is after the optical system shaping, and at the hot spot of two fillet shapes of detecting area formation, spot size is about 1.2 * 0.12mm
2, two hot spots are about 0.1mm in focus place center distance, and particulate will successively obtain two strong scattering peaks by these two hot spots, measure the flight time of particle thus, calculate the particle diameter of particle.Detecting area and optical channel and detector are isolated and sealing with window, avoid extraneous spuious thing to enter detecting area and influence signal.
7, light trapping
Light trap is used for absorbing red laser, eliminates optical noise.
8, detecting area
Diode laser is through the particulate scattering, and scattered light is collected by half ellipsoidal mirror, and its bore is about
Avalanche photo diode (APD) be located at ellipsoidal mirror catoptrical focus place or near, scattering takes place in intersection in particle flux and ruddiness, scatters on the ellipsoidal mirror, the reflected light of ellipsoidal mirror is received by avalanche photodide.Electrical signal processing system:
Flight time scattered light intensity receiving circuit
Photodetector adopts quick avalanche photo diode (APD), it is fast that it has response speed, the advantage that noise is low, its output electric signal is through the sample resistance sampling of the different values of two-way, signal after the sampling amplifies through the amplifier of two-way different gains, and the signal that the buffering back obtains the two-way different gains is sent to follow-up flight time and scattered light intensity treatment circuit.The signal of two-way different gains corresponds respectively to the particle scattering light of different-grain diameter.Signal enters circuit such as preposition amplification, signal Processing time-delay after producing.
By disposal system its APD is detected bimodal signal and carry out continuously processes and displays in real time, so can show the curve map of particle size, quantity, concentration in real time.
Sample introduction and air-flow control circuit
The air-flow control circuit mainly is the flow velocity that obtains particulate and shell gas body by the dynamic pressure that pressure transducer obtains shell stream and total flow.Microcontroller takes the flow velocity of closed-loop control shell stream pump and total flow pump to reach the particulate in laser detection chamber is flowed out and passes in control by nozzle flow velocity by after obtaining total flow, shell stream flow and absolute flow rate.Gasoloid sample gas flow: 1.0 ± 0.22L/min, shell stream (air-casing air-flow): 4.0 ± 0.1L/min, total air flow is: 5.0 ± 0.1L/min.When the particulate particle diameter was 0.5 μ m, maximum detectable concentration was 1500/cm
3, when particle diameter was 10.0 μ m, maximum detectable concentration was 600/cm
3, require the particle coincidence factor less than 10%,
Pressure transducer is connected into the electric bridge form, its output access differential amplifier, and this processing mode helps reducing environment temperature, humidity and The noise.Sensor adopts high precision voltage stabilizer output DC10V power supply.Referring to figure.
The control block diagram of vacuum pump is referring to Fig. 8.
The digital circuit that microcomputer is sent forms simulating signal behind D/A converter, this signal is sent into engine power through buffer compartment and removed to promote vacuum pump after amplifying, and its exhaust velocity is directly proportional with the digital signal that microcomputer is sent.
Claims (6)
1, the laser signal real-time continuous extracting method of airborne particulate suspension comprises:
(1), adopt wavelength coverage at the red semiconductor diode laser of 650-675nm scattering light source as particulate, laser normal incidence behind the collimation lens collimation is to polarization apparatus, by the polarization direction of polarization apparatus adjusting shoot laser, to satisfy of the requirement of vanadic acid yttrium birefringece crystal to the polarization direction; The directional light that expands after restrainting is constant at the vertical direction hot spot behind cylindrical lens A, horizontal direction will be pressed narrow, cylindrical lens B horizontal positioned subsequently, the beam level direction is constant, and vertical direction is pressed narrow, cylindrical lens B is placed in the focus of cylindrical lens A, become the hot spot of the prolate of level on the focal plane, the vertical direction hot spot is Gaussian distribution, and the distance that changes between cylindrical lens A, the B can change in focal plane hot spot horizontal size, regulate the position of cylindrical lens, can change the size and the position thereof of hot spot; Place yttrium vanadate crystal behind the cylindrical lens B, utilize the polarization characteristic of yttrium vanadate crystal, regulate the polarization direction of incident laser, can obtain o light and e light that two beam energies equate, form the hot spot of two fillet shapes in the laser acquisition district;
(2), atmospheric aerosol particle is one by one successively by these two hot spots;
(3), laser is through the particulate scattering, scattered light is collected by half ellipsoidal mirror, and obtains two strong scattering peaks, avalanche photodide is collected the scattered light that scatters from ellipsoidal mirror, the signal that avalanche photodide is collected is sent to electricity system;
(4), light trap is used for absorbing red laser, the elimination optical noise;
Detecting area and optical channel and detector are isolated and sealing with window, avoid extraneous spuious thing to enter detecting area and influence signal.
2, extracting method as claimed in claim 1 is characterized in that the diode laser output power is not less than 28mW, and power fluctuation behind the collimation lens collimation, obtains beam divergence angle less than 5 milliradians less than ± 2%, and spot size is
3mm, the angle of divergence is the output laser of 2mrad.
3, extracting method as claimed in claim 1 is characterized in that detecting area forms the hot spot of two fillet shapes in the laser acquisition district, and spot size is 1.2 * 0.12mm
2, two hot spots are 0.1mm in focus place center distance.
4, extracting method as claimed in claim 1 is characterized in that the bore of ellipsoidal mirror is
50mm.
5, extracting method as claimed in claim 1, it is characterized in that atmospheric aerosol particle is to realize by the following method by these two hot spots successively one by one: a sample channel is set, sample channel is made up of inside and outside two-layer two coaxial pipelines, the inner and outer pipes outlet all has a tapered openings, vertical interval 0.75mm, interior pipe passes through sample flow, flow by shell between the inner and outer pipe, shell stream is the clean gas through filtering, sample flow is a detected sample gas, the flow of keeping shell stream and sample flow be than constant, and shell stream and sample flow are respectively by pumping gas.
6, extracting method as claimed in claim 5, it is characterized in that total flow keeps the constant rate of 5 ± 0.1L/min, keep the shell flow at 5 ± 0.1L/min, the sample flow is at 1 ± 0.2L/min, the pressure of detecting area is lower than pressure of ambient gas 90Torr, and the gas velocity in sample intake passage exit is the hundreds of rice of per second.
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| CN107941665B (en) * | 2017-12-21 | 2024-03-15 | 北京厚力德仪器设备有限公司 | High-resolution aerosol particle size detector |
| DE102018203301A1 (en) * | 2018-03-06 | 2019-09-12 | Robert Bosch Gmbh | Laser-induced incandescence-inducing particle sensor with a confocal arrangement of a laser spot and a thermal radiation spot |
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| CN108693142B (en) * | 2018-06-11 | 2020-10-30 | 重庆大学 | PM2.5 detection method based on optical scattering principle |
| CN113720750B (en) * | 2021-08-31 | 2023-07-28 | 北京航空航天大学 | Optical particle counter |
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| JP2003090796A (en) * | 2001-09-18 | 2003-03-28 | Nippon Steel Corp | Apparatus and method for measurement of substance in air |
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| CN1166600A (en) * | 1996-11-26 | 1997-12-03 | 中国科学院上海光学精密机械研究所 | Optical suspension measuring system |
| WO1999001748A1 (en) * | 1997-07-03 | 1999-01-14 | Hamburger, Robert, N. | Allergen detector system and method |
| CN1397793A (en) * | 2001-07-17 | 2003-02-19 | 株式会社岛津制作所 | Method and device for measuring suspended particle |
| JP2003090796A (en) * | 2001-09-18 | 2003-03-28 | Nippon Steel Corp | Apparatus and method for measurement of substance in air |
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