CN110045391B - Hyperspectral laser radar system for aerosol dimension spectrum measurement - Google Patents
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- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
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- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
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- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
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- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
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Abstract
The invention discloses a hyperspectral lidar system for aerosol scale spectrum measurement, which is characterized in that by using Nd: the YAG laser emitter generates fundamental frequency light which is transmitted by the frequency doubling crystal and the frequency tripling crystal to emit lasers with the wavelengths of 355nm, 532nm and 1064nm, so that laser beams with various wavelengths are emitted into the atmosphere simultaneously; and then, reflected lights with the wavelengths of 355nm, 532nm and 1064nm in the atmosphere reflection echo are separated by using a telescope, a color separation plate and a narrow-band interference filter, and the separated reflected lights are subjected to separation of atmospheric molecule Rayleigh scattering signals and aerosol meter scattering signals through different light paths, so that the hyperspectral lidar can accurately detect the physical characteristics and time-space distribution of the reflected lights with various wavelengths.
Description
Technical Field
The invention belongs to the field of atmospheric science, and particularly relates to a hyperspectral laser radar-based detection method for aerosol scale spectrum measurement.
Background
In a broad sense, atmospheric aerosol refers to various non-gaseous particles suspended in the atmosphere below about 100um in diameter, such as smoke, dust, microorganisms, sulfates, nitrates, and the like. Atmospheric aerosols have a major impact on light transmission, the environment, climate and human health. For example, it can affect the surface temperature by absorbing and scattering the sun; secondly, the aerosol is used as a cloud condensation nucleus in the cloud forming process, so that the capability of the cloud for absorbing and reflecting solar radiation can be changed, the optical characteristics of the cloud, the cloud cover and the service life of the cloud are influenced, and further precipitation is influenced; a large amount of coal is combusted again, and industrial waste gas is discharged to generate a large amount of aerosol, the aerosol contains a large amount of greenhouse gas components, so that the global greenhouse effect is intensified, and meanwhile, acid rain is caused to further worsen the environment; the aerosol particles which are most harmful to human beings are PM2.5, PM2.5 can directly enter the respiratory tract of a human body and is deposited and is not easy to be discharged out of the human body, and PM2.5 is usually generated after carcinogenic substances are combusted, so that various diseases can be induced and the health of the human body is seriously harmed after the aerosol particles are in the environment for a long time; therefore, the method has important scientific and practical significance for the accurate detection of the physical characteristics and the time-space distribution of the aerosol.
As an important remote sensing means, the lidar is an optical device that obtains the properties of a target by analyzing an echo signal of the interaction between a remote target and a laser beam. Due to the advantages of long detection distance, high detection precision and the like, the laser radar becomes indispensable equipment in the field of aerosol detection. However, the detection data of the existing single-wavelength laser radar can only reflect the aerosol characteristics of a certain specific scale, and therefore, the single-wavelength laser radar cannot meet the requirement of researching the atmospheric aerosol characteristics in a large-scale range.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide a hyperspectral lidar system capable of detecting reflected light with various wavelengths simultaneously.
The invention adopts the following technical scheme for solving the technical problems:
the invention provides a hyperspectral lidar system for aerosol scale spectrum measurement, which comprises a lidar transmitting system, a laser radar system and a control system, wherein the lidar transmitting system is used for transmitting laser beams with different wavelengths into the atmosphere through a full mirror;
the receiving system is used for receiving the scattered light beams which return after being scattered by the atmosphere;
the light splitting system is used for separating an atmospheric molecular Rayleigh scattering signal from an aerosol Mie scattering signal of the scattered light beam received by the receiving system and transmitting the atmospheric molecular Rayleigh scattering signal and the aerosol Mie scattering signal to the master control system;
and the master control system is used for carrying out data analysis on the received scattered signals.
The preferred technical scheme of the invention is as follows: the laser radar transmitting system comprises a laser, a frequency doubling crystal, a frequency tripling crystal and a first full-reflecting mirror; the fundamental frequency light generated by the laser respectively passes through the frequency doubling crystal and the frequency tripling crystal, and simultaneously emits laser with the repetition frequency of 100Hz and the wavelengths of 355nm, 532nm and 1064nm to vertically enter the atmosphere through the first total reflection mirror.
The preferred technical scheme of the invention is as follows: the receiving system comprises a telescope, a small hole, a first converging lens and a second total reflection mirror; the receiving system vertically receives atmosphere backscattered light by using a telescope, the backscattered light is collimated by the small hole and the first converging lens to become parallel light, and the parallel light is reflected to the light splitting system by the second full-reflecting mirror.
The preferred technical scheme of the invention is as follows: the light splitting system comprises a first dichroic filter, a second dichroic filter, a third dichroic filter, a first narrow-band interference filter, a second narrow-band interference filter, a third narrow-band interference filter, a polarization beam splitter, a lambda/4 wave plate, an FP etalon, a second converging lens, a third converging lens, a fourth converging lens, a fifth converging lens, a sixth converging lens, an iodine molecule absorption filter, an avalanche photodiode, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector and a fourth photoelectric detector; the light splitting system separates a reflected light beam with the wavelength of 355nm from a back scattering light beam through a first dichroic filter and a first narrow-band interference filter, the separated reflected light with the wavelength of 355nm is separated into parallel polarization signals through a polarization beam splitter, wherein a part of the parallel polarization signals are converged through a lambda/4 wave plate, an FP etalon and a second converging lens and enter a first photoelectric detector for photoelectric signal conversion and recording, and a light path channel is an aerosol channel; the other part of the parallel polarization signals are reflected again by the FP etalon and return to the lambda/4 wave plate, the polarization direction is rotated by 90 degrees, the parallel polarization signals are reflected again by the polarization beam splitter and converged by the third converging lens to enter the second photoelectric detector for photoelectric signal conversion and recording, and the light path channel is a first molecular channel; the light splitting system separates a reflected light beam with the wavelength of 532nm from a backward scattering light beam through a second dichroic filter and a second narrow-band interference filter, wherein a part of the reflected light with the wavelength of 532nm is converged by a fourth converging lens and enters a fourth photoelectric detector for photoelectric signal conversion and recording, and a light path channel is a comprehensive channel; the other part of reflected light with the wavelength of 532nm is converged by an iodine molecule absorption filter through a fifth converging lens and enters a third photoelectric detector for photoelectric signal conversion and recording, and the light path channel is a second molecular channel; the light splitting system separates a reflected light beam with the wavelength of 1064nm from a backward scattering light beam through a third dichroic filter and a third narrow-band interference filter, the separated scattered light enters an avalanche photodiode through a sixth converging lens to perform photoelectric signal conversion and recording, and the light path channel is a third sub-channel.
The preferred technical scheme of the invention is as follows: the master control system comprises a signal acquisition module and a computer; the main control system collects data recorded by the first photoelectric detector, the second photoelectric detector, the third photoelectric detector, the fourth photoelectric detector and the avalanche photodiode through the signal collection module and transmits the data to the computer for data analysis.
The preferred technical scheme of the invention is as follows: the laser is Nd: YAG type laser.
The preferred technical scheme of the invention is as follows: the telescope is a Cassegrain telescope with the caliber of 400mm and the focal length of 2000mm.
The preferred technical scheme of the invention is as follows: the signal acquisition module is a NI Pcle6363 signal acquisition module.
The preferred technical scheme of the invention is as follows: the photodetector is an EMI9214 model photodetector.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
the invention uses Nd: the YAG laser transmitter generates fundamental frequency light which is transmitted by the frequency doubling crystal and the frequency tripling crystal to lasers with the wavelengths of 355nm, 532nm and 1064nm, so that laser beams with various wavelengths are simultaneously transmitted into the atmosphere, and the detection range is wider compared with that of a traditional single-wavelength laser radar.
According to the invention, reflected lights with the wavelengths of 355nm, 532nm and 1064nm in the atmosphere reflection echo are separated by using the telescope, the color separation plate and the narrow-band interference filter, and the separated reflected lights are subjected to atmospheric molecule Rayleigh scattering signals and aerosol meter scattering signals separation through different light paths, so that the hyperspectral laser radar can accurately detect the physical characteristics and time-space distribution of the reflected lights with various wavelengths, and compared with the traditional single-wavelength laser radar, the detection result is more stable and accurate.
Drawings
FIG. 1 is a schematic diagram of a hyperspectral lidar system of the invention;
FIG. 2 is a transmitted light spectrum of the FP interferometer reflection field for atmospheric backscatter signals;
FIG. 3 is a schematic diagram of the absorption principle of an iodine molecular absorption filter;
FIG. 4 is a Tikhonov regularization inversion procedure.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the present invention is a hyperspectral lidar system for aerosol scale spectrum measurement, and mainly includes a lidar transmission system, a light splitting system, a receiving system, and a master control system.
The laser radar transmitting system comprises a laser, a frequency doubling crystal, a frequency tripling crystal and a first full-reflecting mirror.
The receiving system comprises a telescope, a small hole, a first converging lens and a second total reflection mirror.
The light splitting system comprises a first dichroic filter, a second dichroic filter, a third dichroic filter, a first narrow-band interference filter, a second narrow-band interference filter, a third narrow-band interference filter, a polarization beam splitter, a lambda/4 wave plate, an FP etalon, a second converging lens, a third converging lens, a fourth converging lens, a fifth converging lens, a sixth converging lens, an iodine molecule absorption filter, an avalanche photodiode, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector and a fourth photoelectric detector.
And the master control system receives the data acquired by the signal acquisition module for data analysis.
The hyperspectral lidar system for the aerosol dimension spectrum measurement has the following specific working process:
step one, basic frequency light generated by a laser respectively passes through a frequency doubling crystal and a frequency tripling crystal, and simultaneously emits laser with the repetition frequency of 100Hz and the wavelengths of 355nm, 532nm and 1064nm to vertically enter the atmosphere through a first total reflection mirror.
And step two, the telescope vertically receives atmosphere backward scattering light, the backward scattering light is collimated by the small hole and the first converging lens to become parallel light, and the parallel light is reflected to the light splitting system by the second full-reflecting mirror.
Thirdly, the backscattered echo signal with the wavelength of 355nm, which is separated by the first dichroic filter and the first narrow-band interference filter, is separated into a parallel polarized light signal and a vertical polarized light signal by a polarization beam splitter, wherein a part of the parallel polarized signal is converged by a lambda/4 wave plate, an FP etalon and a second converging lens to enter a first photoelectric detector, and is an aerosol channel; the rest most of the parallel polarization signals are reflected by the FP etalon again and return to the lambda/4 wave plate, the polarization direction is rotated by 90 degrees, and the signals are reflected again by the polarization beam splitter and converged by the third converging lens to enter the second photoelectric detector to form a first molecular channel; the data collected by the first photoelectric detector and the second photoelectric detector are transmitted to the main control system through the signal collecting module for data analysis.
Fourthly, backward scattering echo signals with the wavelength of 532nm are separated by a second dichroic filter and a second narrow-band interference filter, wherein a part of the backward scattering echo signals are converged by a fourth converging lens to enter a fourth photoelectric detector and form a comprehensive channel; the other part of the backscattered echo signals are converged by an iodine molecule absorption filter through a fifth converging lens to enter a third photoelectric detector, and the second part of the backscattered echo signals are second molecular channels; and the data acquired by the third photoelectric detector and the fourth photoelectric detector are transmitted to the master control system through the signal acquisition module for data analysis.
Step five, backward scattering echo signals with the wavelength of 1064nm, which are separated by a third dichroic filter and a third narrow-band interference filter, are converged into an avalanche photodiode through a sixth converging lens; and the data acquired by the avalanche photodiode is transmitted to a master control system through a signal acquisition module for data analysis.
And step six, the master control system collects data recorded by the first photoelectric detector, the second photoelectric detector, the third photoelectric detector, the fourth photoelectric detector and the avalanche photodiode through the signal collection module and transmits the data to a computer for data analysis.
As a preferred embodiment of the present invention, a laser employs a Nd: YAG laser. The telescope is a Cassegrain telescope with the caliber of 400mm, and the focal length of the Cassegrain telescope is 2000mm. The photodetector is an EMl9214 photomultiplier tube. The acquisition module adopts an acquisition card of NI Pcle6363 model. The free spectral range of the FP etalon is 2GHz. The iodine molecule absorption line of the iodine molecule absorption filter is 1109, and the peak wavelength of the iodine molecule absorption filter is 532.26nm.
As shown in fig. 2, a transmission spectrum of the FP interferometer reflection field for the atmospheric backscatter signal is shown, the dotted line represents the rayleigh scatter signal, the dotted line represents the mie scatter signal, and the solid line represents the FP interferometer transmission spectrum curve. As can be seen from the figure, the broadening is small because the spectral width of aerosol scattering depends on the brownian motion of the atmospheric aerosol particles, and can be generally approximated as the spectral line width of a divergent laser pulse, while the molecular scattering spectrum is the doppler broadening due to the thermal motion of atmospheric molecules, which can reach the GHz order of magnitude. The transmittance curve of the FP is combined, so that aerosol rice scattering signals can be restrained and cannot penetrate through the FP etalon after the atmosphere backscattering signals pass through the FP interferometer, most Rayleigh scattering signals penetrate through the FP etalon, only a few rice scattering signals pass through the FP etalon, and high spectrum light splitting of the signals is achieved.
As shown in fig. 3, which is a schematic diagram of the absorption principle of the iodine molecular absorption filter, the thin solid line is an iodine absorption line, i.e., a transmittance curve, the dotted line represents the superposition of the aerosol and the molecular scattering spectrum, the thick solid line represents the spectrum after passing through the iodine molecular absorption filter, the aerosol scattering is filtered, and the molecular scattering part passes through.
A 532nm backscattering signal received by the telescope is divided into two beams, one beam of light passes through the iodine molecule absorption cell, the rice scattering component in the beam of light is absorbed, and the Rayleigh scattering component partially penetrates through the iodine molecule absorption cell and is detected by the PMT to serve as a molecule channel; the other beam of light is directly detected by the PMT as an integrated channel. Signals of the molecular channel and the integrated channel are respectively marked as s mol (z) and s com (z)：
s mol (z)＝η mol ·[f mol (z)·N m (z)+f a ·N a (z)] (1)
s com (z)＝η com ·[N m (z)+N a (z)] (2)
In the formula: z is the height relative to the position of the laser radar; eta mol And η com Respectively a molecular channel and a comprehensive channelThe detection efficiency of (a), including all optical and electronic constants except the iodine absorption cell; n is a radical of m (z) and N a (z) a molecular rayleigh scatter signal and an aerosol rice scatter signal, respectively, scattered at a height z and received by the system; f. of m (z) is the transmittance of atmospheric molecular scattering echoes at the height z through an iodine pool, which is the convolution of a Rayleigh scattering spectrum and an iodine molecular absorption spectrum in a frequency domain; f. of a The transmittance of the aerosol meter scattered echo through the iodine cell, approximately equal to the transmittance at the center of the iodine absorption line, is a small amount independent of height.
By introducing laser into the receiving system for frequency scanning and combining the molecular scattering spectral lines at different heights, the calibration coefficients C of the molecular channel and the comprehensive channel can be calculated mm (z) and C am ：
C mm (z)＝f m (z)·η mol /η com (3)
C am ＝f a ·η mol /η com (4)
Therefore, the rayleigh scatter signal and the mie scatter signal can be extracted from the original signal:
the data analysis process of the step six adopts an inversion method, and the specific process is as follows:
the power of the received backscatter signal can be expressed in terms of the radar equation:
wherein P (r) is the power of the scattered signal at the height r; p 0 Is the average power of the pulse of the emitted laser light; η is the power of the receiver; a isA receiving area; o (r) is the geometrical overlapping coefficient of the optical paths of the transmitter and the receiver; c is the speed of light; t is the width of the laser pulse; β (r) and α (r) are the atmospheric backscattering coefficient and extinction coefficient at altitude, respectively.
The actual atmospheric backscattering coefficient and the atmospheric extinction coefficient contain a molecular scattering moiety and an aerosol scattering moiety. The radar equation contains two unknowns, β and α, which can be expressed as:
β＝β mol +β aer (8)
α＝α mol,sca +α mol,abs +α aer,sca +α aer,abs (9)
wherein alpha is mol,abs In the normal case, it can be assumed that 0, α aer ＝α aer,sca +α aer,abs 。β mol Proportional to the atmospheric density, the atmospheric temperature and pressure distribution data above the standard atmospheric model or observation point can be obtained. Alpha is alpha mol,sca Can be prepared from mol The relationship between is obtained, satisfy
α mol,sca ＝β mol ×(8/3)πsr (10)
The received separated atmospheric molecule signal and aerosol signal are respectively
In the formula, K mol And K aer All system constants which are irrelevant to the measured height are respectively contained; f. of am And f mm Respectively the passing rates of aerosol signals and molecular signals in the molecular channel; f. of aa And f ma The respective transit rates of the aerosol signal and the molecular signal in the aerosol channel can be obtained by a calibration process before the experiment. Beta can be obtained by inversion through the formulas (11) and (12) aer And alpha aer The value of (c).
One advantage of the present invention is that extinction and scattering coefficients of multiple wavelengths can be obtained, and the aerosol particle spectra are inverted using a numerical approximation idea in combination with a Honnouv regularization algorithm, as shown in FIG. 4.
The inverse problem of the particle spectrum distribution can be expressed by Fredholm integral equation, and the extinction coefficient and the backscattering coefficient can be expressed as
r represents the particle radius, m = mr + imi represents the negative refractive index of the particle, mr represents the real part, mi represents the imaginary part, λ i Denotes the wavelength, K α And K β Representing the extinction and the back-kernel functions, respectively, can be calculated by Mie scattering theory, f (r) is the particle spectrum, (13) and (14) can be written as
(15) The method is a first type integral equation, is not easy to solve, and can obtain aerosol micro physical characteristic parameters by inverting aerosol parameters by utilizing a Tikhonov approximation algorithm.
The volume spectrum can be expressed as
Substituting (16) into (15) to obtain
In the formula, g p The type of optical data, i.e., the extinction coefficient α and the backscattering coefficient β of the aerosol; b is j (r) is a triangular basis function, j =1, \8230;, 5 corresponds to a basis function, ∈ math (r) is the calculation error; p = (i, λ) is data type and wavelength, i = α, β, α represents aerosol extinction coefficient, β represents aerosol backscattering coefficient; q p (r，m，λ i ) Efficiency factor for all data points; a. The pj And (m) is a kernel function matrix obtained by calculation.
The determination of the spectral distribution of the aerosol particles can therefore be attributed to the weighting factor w j And (4) solving. Substituting (18) and (19) into (17), g p Can be expressed as
g＝Aw+error p (20)
Where g and w are the column vectors of p × 1 and n × 1, respectively, and A is a matrix of p × n. Multiplying both sides by a-1 simultaneously can be w = a -1 g+error′ (21)
The expression after regularizing the above formula is
In the formula, gamma is a Lagrange multiplier and is also called a regularization parameter, and the right selection of the Lagrange multiplier gamma can enable a weight factor w to be j The error is minimum, the Lagrange multiplier solving method is many, and the cross verification method is selected for solving, so that the method is simple and easy to operate. H pj To smooth the matrix, the choice of matrix is determined by the desired optical parameters.
Let gamma 0 Has a value of gamma min ～γ max Typically taking a number between 103 and 105. From this, the volume spectral distribution can be found, and the expression is shown in (23):
the above examples are preferred embodiments of the present invention, but the present invention is not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and they are included in the scope of the present invention.
In the description of the present invention, it is to be understood that the terms indicating an orientation or positional relationship are based on the orientation or positional relationship shown in the drawings only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Claims (2)
1. A hyperspectral lidar system for measurement of aerosol dimensions spectra, characterized in that: comprises that
The laser radar transmitting system is used for transmitting laser beams with different wavelengths into the atmosphere through the full-reflection mirror;
the receiving system is used for receiving the scattered light beams which return after being scattered by the atmosphere;
the light splitting system is used for separating an atmospheric molecular Rayleigh scattering signal from an aerosol Mie scattering signal of the scattered light beam received by the receiving system and transmitting the atmospheric molecular Rayleigh scattering signal and the aerosol Mie scattering signal to the master control system;
the main control system is used for carrying out data analysis on the received scattering signals;
the laser radar transmitting system comprises a laser, a frequency doubling crystal, a frequency tripling crystal and a first full-reflecting mirror; the laser is used for generating fundamental frequency light, the fundamental frequency light respectively passes through the frequency doubling crystal and the frequency tripling crystal, and laser with the repetition frequency of 100Hz and the wavelengths of 355nm, 532nm and 1064nm is simultaneously emitted and vertically enters an atmosphere layer through the first total reflection mirror;
the receiving system comprises a telescope, a small hole, a first converging lens and a second total reflection mirror; the telescope vertically receives atmosphere backward scattering light, the backward scattering light is collimated by the small hole and the first converging lens to become parallel light, and the parallel light is reflected to the light splitting system by the second full-reflection mirror;
the master control system comprises a signal acquisition module and a computer; the signal acquisition module is used for acquiring data recorded by the first photoelectric detector, the second photoelectric detector, the third photoelectric detector, the fourth photoelectric detector and the avalanche photodiode and transmitting the data to the computer for data analysis;
the signal acquisition module acquires a second molecular channel signal fed back by a third photoelectric detector and an integrated channel signal fed back by a fourth photoelectric detector, and the signals of the molecular channel and the integrated channel are respectively recorded as s mol (z) and s com (z):
s mol (z)＝η mol ·[f mol (z)·N m (z)+f a ·N a (z)] (1)
s com (z)＝η com ·[N m (z)+N a (z)] (2)
In the formula: z is the height relative to the position of the laser radar; eta mol And η com The detection efficiencies of the molecular channel and the comprehensive channel respectively comprise all optical and electronic constants except the iodine absorption cell; n is a radical of m (z) and N a (z) a molecular rayleigh scatter signal and an aerosol rice scatter signal, respectively, scattered at a height z and received by the system; f. of mol (z) is the transmittance of atmospheric molecular scattering echoes at height z through an iodine cell, which is the convolution of the rayleigh scattering spectrum and the iodine molecular absorption spectrum in the frequency domain; f. of a The transmittance of aerosol meter scattering echo through an iodine pool is approximately equal to the transmittance of an iodine absorption spectral line center and is a small quantity independent of height;
by introducing laser into the receiving system for frequency scanning and combining the molecular scattering spectral lines at different heights, the calibration coefficients C of the molecular channel and the comprehensive channel can be calculated mm (z) and C am :
C am ＝f a ·η mol /η com (4)
Therefore, the rayleigh scatter signal and the mie scatter signal can be extracted from the original signal:
an inversion method is adopted in the data analysis process, and the specific process is as follows:
the power of the received backscatter signal can be expressed in terms of the radar equation:
wherein P (r) is the power of the scattered signal at the height r; p is 0 Is the average power of the pulses of the emitted laser light; η is the power of the receiver; a is the receiving area; o (r) is a geometrical overlapping coefficient of the optical paths of the transmitter and the receiver; c is the speed of light; t is the width of the laser pulse; β (r) and α (r) are the atmospheric backscattering coefficient and extinction coefficient at altitude, respectively;
the actual atmospheric backscattering coefficient and the atmospheric extinction coefficient comprise a molecular scattering part and an aerosol scattering part;
the radar equation contains two unknowns, β and α, which can be expressed as:
β＝β mol +β aer (8)
α＝α mol,sca +α mol,abs +α aer,sca +α aer,abs (9)
wherein alpha is mol,abs Under normal circumstances may be falseIs set to 0, alpha aer ＝α aer,sca +α aer,abs ,β mol Proportional to the atmospheric density, and can be obtained through the atmospheric temperature and pressure distribution data above a standard atmospheric model or an observation point;
α mol,sca can be composed of beta mol The relationship between them is obtained, satisfying:
α mol,sca ＝β mol ×(8/3)πsr (10)；
the received separated atmospheric molecule signal and aerosol signal are respectively:
in the formula, K mol And K aer All system constants which are irrelevant to the measurement height are respectively contained; f. of am And f mm Respectively the passing rates of aerosol signals and molecular signals in the molecular channels; f. of aa And f ma Respectively the passing rates of aerosol signals and molecular signals in the aerosol channel, and beta can be obtained by inversion through formulas (11) and (12) aer And alpha aer The value of (c).
2. The hyperspectral lidar system for measurement of aerosol dimensions spectrum according to claim 1, characterized in that extinction and scattering coefficients of multiple wavelengths can be obtained, the aerosol particle spectrum is inverted by numerical approximation idea in combination with Honnough regularization algorithm; the inverse problem of the particle spectrum distribution can be expressed by using a Fredholm integral equation, and then the extinction coefficient and the backscattering coefficient can be expressed as follows:
r represents the particle radius, m = mr + imi represents the negative refractive index of the particle, mr represents the real part, mi represents the imaginary part, λ i Denotes the wavelength, K α And K β Representing the extinction and the back-kernel functions, respectively, can be calculated by Mie scattering theory, f (r) is the particle spectrum, (13) and (14) can be written as:
(15) The method is a first type integral equation which is difficult to solve, and aerosol micro physical characteristic parameters can be obtained by inverting aerosol parameters by utilizing a Tikhonov approximation algorithm;
the volume spectrum can be expressed as:
substituting (16) into (15) yields:
in the formula, g p The type of optical data, i.e., the extinction coefficient α and the backscattering coefficient β of the aerosol; b is j (r) is a triangular basis function, j =1, \8230;, 5 corresponds to a basis function，ε math (r) is the calculation error; p = (i, λ) is data type and wavelength, i = α, β, α represents aerosol extinction coefficient, β represents aerosol backscattering coefficient; q p (r,m,λ i ) Efficiency factor for all data points; a. The pj (m) is a kernel function matrix obtained by calculation;
the determination of the spectral distribution of the aerosol particles can therefore be attributed to the weighting factor w j Solving;
substituting (18) and (19) into (17), g p Can be expressed as:
g＝Aw+error p (20)
where g and w are the column vectors of p × 1 and n × 1, respectively, a is the matrix of p × n, and multiplying both sides by a-1 can be:
w＝A -1 g+error′ (21)；
the expression after regularizing the above formula is:
in the formula, gamma is a Lagrange multiplier and is also called a regularization parameter, and the right selection of the Lagrange multiplier gamma can enable a weight factor w to be j The error is minimum, the Lagrange multiplier solving method is many, and the cross verification method is selected for solving the problem because the method is simple and easy to operate and H pj To smooth the matrix, the selection of the matrix is determined according to the required optical parameters;
let gamma 0 Has a value of gamma min ～γ max Generally, a number between 103 and 105 is taken, so that the volume spectrum distribution can be obtained, and the expression (23) is shown as follows:
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103308926A (en) * | 2013-06-18 | 2013-09-18 | 浙江大学 | Laser radar set with high spectral resolution |
| CN104777487A (en) * | 2015-04-28 | 2015-07-15 | 南京信息工程大学 | Atmospheric aerosol optical property measuring method and laser radar system |
| CN104880711A (en) * | 2015-05-18 | 2015-09-02 | 中国科学院合肥物质科学研究院 | Single-wavelength four-Raman laser radar detection system and detection method |
| CN106019312A (en) * | 2016-08-04 | 2016-10-12 | 浙江大学 | Multi-longitudinal-mode high-spectral-resolution lidar based on interference spectrum frequency detector |
| CN108303706A (en) * | 2018-03-12 | 2018-07-20 | 南京信息工程大学 | A kind of aerosol optical parameter detection method and EO-1 hyperion Airborne Lidar examining system |
| CN207991998U (en) * | 2018-04-16 | 2018-10-19 | 成都信息工程大学 | A kind of airborne back scattering cloud particle survey meter and meteorological detecting devices |
-
2019
- 2019-04-24 CN CN201910337146.8A patent/CN110045391B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103308926A (en) * | 2013-06-18 | 2013-09-18 | 浙江大学 | Laser radar set with high spectral resolution |
| CN104777487A (en) * | 2015-04-28 | 2015-07-15 | 南京信息工程大学 | Atmospheric aerosol optical property measuring method and laser radar system |
| CN104880711A (en) * | 2015-05-18 | 2015-09-02 | 中国科学院合肥物质科学研究院 | Single-wavelength four-Raman laser radar detection system and detection method |
| CN106019312A (en) * | 2016-08-04 | 2016-10-12 | 浙江大学 | Multi-longitudinal-mode high-spectral-resolution lidar based on interference spectrum frequency detector |
| CN108303706A (en) * | 2018-03-12 | 2018-07-20 | 南京信息工程大学 | A kind of aerosol optical parameter detection method and EO-1 hyperion Airborne Lidar examining system |
| CN207991998U (en) * | 2018-04-16 | 2018-10-19 | 成都信息工程大学 | A kind of airborne back scattering cloud particle survey meter and meteorological detecting devices |
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