CN205786312U - A kind of aerosol phase function observation system - Google Patents

Abstract

The utility model discloses an aerosol phase function observation system. The aerosol phase function observation system of the utility model includes: a laser emitting unit, an optical trap, a turbidity meter, a scattering signal receiver and a computer; a turbidity meter is installed below the laser beam, and the backscattering coefficient of the aerosol hemisphere is measured; Next to the laser beam and at the same position as the laser beam, a scattering signal receiver is installed; the utility model combines the signal obtained by the CCD camera with the backscattering coefficient of the aerosol hemisphere measured by the turbidimeter to obtain the aerosol phase function, Scattering information at different angles can be obtained at the same time, avoiding the influence of the change of aerosol scattering properties over time; the observation system of the utility model is simple and effective, and the cost is low, which provides a new technology for the observation of aerosol phase function It provides support for the inversion of related instruments for remote sensing observation of aerosol optical properties.

Description

An aerosol phase function observation system

technical field

The utility model relates to atmospheric detection technology, in particular to an aerosol phase function observation system.

Background technique

Aerosols are tiny particles suspended in the air, often referred to simply as atmospheric particulate matter. When radiation is transmitted in the atmosphere, it is scattered by different components such as gases and aerosols in the atmosphere, and its intensity, transmission direction, and polarization state will all change. In most cases, since solar radiation is natural light, the scattered light in the atmosphere is distributed axisymmetrically. Therefore, this distribution can be described by a single plane angle, 0 degrees means that the scattered light is forward scattered in the same direction as the incident light, 180 degrees means that the scattered light is back scattered in the opposite direction to the incident light, and the distance between the scattered light and the incident light is The included angle is the scattering angle. The phase function is defined as a physical quantity describing the distribution of scattered light intensity at different scattering angles.

In recent years, some studies have built instruments for observing aerosol phase functions, and carried out indoor experiments and field observation experiments. The light sources used in these instruments are all lasers, because only lasers with small divergence angles can meet the needs of measuring phase functions.

The first design is to install a photomultiplier tube on the mechanical arm so that it rotates around a point in the optical path in the plane where the laser is located to receive scattered signals of different scattering angles; the second design is to make the gas path perpendicular to The light paths meet at one point, and then a lot of photodiodes are installed around this point in the plane where the laser is located, and each photodiode receives scattered signals with different scattering angles; the third design is to place two parabolic reflectors next to the light path, Let the light scattered from the same point to different angles pass through two mirrors and then re-converge at a new point. A rotatable flat mirror is placed at this point, and by rotating the angle of the mirror, the scattering signals of different scattering angles are reflected into the photomultiplier tube; the fourth design is to open a hole inside an ellipsoid mirror to allow the light path to pass through, and the scattering After being reflected by the ellipsoidal mirror, the light passes through a pipeline and reaches the photomultiplier tube, and by rotating the pipeline, scattered light signals with different scattering angles can be reflected and then reach the photomultiplier tube. Some of these researches on the phase function of aerosols are carried out on aerosol particles in the laboratory, and some are used to observe cloud droplets and ice crystals whose particle size is much larger than that of aerosol particles in aircraft observations, but are not used in aerosol particles. Sol field observation.

Utility model content

Aiming at the deficiencies in the prior art above, the utility model proposes an aerosol phase function observation system, which simultaneously detects aerosol scattered light at different angles to obtain the aerosol phase function, reduces system complexity and reduces instrument cost.

The aerosol phase function observation system of the utility model includes: a laser emitting unit, an optical trap, a turbidity meter, a scattering signal receiver and a computer; wherein, the laser emitting unit emits continuous laser light in the horizontal direction; Trap to absorb the remaining laser light; install a turbidity meter below the laser beam, and align the air inlet of the turbidity meter with the laser beam; install a scattered signal receiver next to the laser beam and at the same height as the laser beam; the scattered signal receiver The detector includes a wide-angle lens, a laser filter and a CCD camera. The scattered light of the laser beam scattered by gases and aerosols in the atmosphere is gathered by the wide-angle lens, filtered by the laser filter, and received by the CCD camera; the turbidimeter and the CCD camera are respectively connected to the computer.

The laser emitting unit includes a solid-state laser and a frequency-doubling crystal; the solid-state laser uses a solid-state laser material as a light-emitting substance, and the emitted laser light becomes a frequency-doubled laser after passing through a frequency-doubling crystal, and the laser beam is emitted in the horizontal direction.

The wide-angle lens, the laser filter and the CCD camera constitute the scattering signal receiver, and the laser filter is installed between the wide-angle lens and the CCD camera; the wide-angle lens adopts the equiangular projection method, that is, the solid angle of the subject and the area it occupies on the screen In direct proportion, the scattered light in a wide range is gathered; the background signal unnecessary for data analysis is filtered out through the laser filter; the scattered light signal of the laser beam gathered by the atmosphere through the wide-angle lens is received by the CCD camera and imaged, and the CCD camera After each pixel receives photons, it generates electric charges and converts them into electrical signals.

The laser emitting unit emits parallel continuous laser light, and the laser beam enters the optical trap after passing through a section of optical path; next to the laser beam, place a scattering signal receiver at the same height as the laser beam, and align it with the direction of the laser beam, using the principle of light scattering Capture the scattered light signal with the CCD imaging principle; convert the light signal into an electrical signal, and then transmit it to the computer to complete the imaging control and signal acquisition; then combine with the backscattering coefficient of the aerosol hemisphere measured by the turbidity meter, Then the aerosol phase function is obtained.

Advantage of the utility model:

The utility model combines the signal obtained by the CCD camera with the backscattering coefficient of the aerosol hemisphere measured by the turbidity meter to obtain the aerosol phase function, which can simultaneously obtain the scattering information of different angles, and avoids the change of the aerosol scattering properties with time affect the results; the observation system of the utility model is simple and effective, and the cost is low, which provides a new technical means for the observation of the aerosol phase function, and provides support for the inversion of related instruments for remote sensing observation of aerosol optical characteristics.

Description of drawings

Fig. 1 is the side view of the aerosol phase function observation system of the present utility model;

Fig. 2 is a top view of the aerosol phase function observation system of the present invention.

detailed description

Below in conjunction with accompanying drawing, through specific embodiment, further set forth the utility model.

As shown in Fig. 1 and Fig. 2, the aerosol phase function observation system of the present embodiment comprises: laser emitting unit A, light trap D, nephelometer C, scattering signal receiver B and computer; Wherein laser emitting unit A emits Continuous laser in the horizontal direction, install an optical trap D at the end of the laser beam to absorb the remaining laser light; install a turbidimeter C below the laser beam, align the air inlet C1 of the turbidimeter with the laser beam, and measure the aerosol hemisphere Backscatter coefficient; Next to the laser beam and at the same position as the laser beam height, the scattered signal receiver B is installed; the scattered signal receiver B includes a wide-angle lens B1, a laser filter B2 and a CCD camera B3, and the wide-angle lens B1 will be within a wide range The laser beam is converged by the scattered light of the atmosphere, and after being filtered by the laser filter B2, the optical signal is received by the CCD camera B3 and converted into an electrical signal; the turbidimeter C and the CCD camera B3 are respectively connected to the computer.

In this embodiment, the laser of the laser emitting unit adopts solid laser material to emit continuous laser light with an emission wavelength of 1064 nanometers; after frequency doubling, a laser beam with a wavelength of 532 nanometers is emitted; the laser beam is emitted along the horizontal direction.

The observation method of the aerosol phase function observation system of the present embodiment comprises the following steps:

1) Collect a dark frame image, that is, use a baffle to block the CCD camera for detection.

2) Turn on the laser, open the baffle for image acquisition, read the grayscale data of each pixel on the image, and then subtract the grayscale data corresponding to the dark frame image to obtain the atmospheric scattering of the laser beam with the dark current and noise removed Image of light, atmosphere including gases and aerosols.

3) A linear fitting method is used to fit the central axis of the image of the scattered light of the laser beam.

4) Obtain the scattering angle θ of the scattered light of the laser beam corresponding to each pixel on the central axis:

a) adjust the angle of the CCD camera so that the image of the scattered light of the laser beam through the atmosphere passes through the central point of the pixel matrix of the CCD camera;

b) Use the reference object method to mark the image position corresponding to the scattering angle of the scattered light scattered by the laser beam through the atmosphere at 90°;

c) According to the image position corresponding to the central point and the 90° scattering angle, combined with the focal length f of the wide-angle lens, calculate the scattering angle of the scattered light of the laser beam corresponding to the central point through the atmosphere;

d) According to the scattering angle corresponding to the center point, the image position corresponding to the 90° scattering angle, and the focal length f of the wide-angle lens, calculate the corresponding relationship between the scattering angle of the scattered light of the entire laser beam and the position on the image, so as to obtain the position of each pixel Corresponding to the scattering angle θ of the scattered light of the laser beam.

5) Divide the fitted central axis into multiple files with one pixel as the step length, and make a line segment perpendicular to the central axis on the corresponding pixel point of each file and take the pixel point on the central axis as the midpoint, select The appropriate length of the line segment enables the signals related to the scattered light of the laser beam to be included in these pixels, and the gray value corresponding to each pixel in the line segment is obtained, and the normal distribution function is used for the gray value of each file Fitting is performed to obtain the scattered light signal intensity of the atmosphere corresponding to each pixel, and the normal distribution function satisfies:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

Among them, x is the pixel coordinates in the line segment perpendicular to the central axis, μ is the coordinates of the midpoint of the line segment, (x-μ) is the distance from each pixel point in the line segment to the midpoint, and σ is the standard of normal distribution I ₀ is the sky background radiance received by the CCD camera, and the signal intensity of the scattered light of the laser beam corresponding to this line segment is I.

6) According to the scattering angle of the scattered light corresponding to each pixel point and the signal intensity of the scattered light in the atmosphere, the variation I(θ) of the signal intensity with the scattering angle is obtained.

7) Obtain the change of the signal intensity of the aerosol with the scattering angle I _aero (θ):

a) Obtain the aerosol hemispherical backscattering coefficient by measuring with a nephelometer, and combine the gas hemispherical backscattering coefficient to obtain the ratio of the hemispheric backscattering coefficient of the aerosol to the gas;

b) Integrating the backscattering signals at different angles within the hemisphere to obtain the integrated intensity of the total hemispheric backscattering signals for gases and aerosols;

c) The integral intensity of the total hemispherical backscattering signal is multiplied by the ratio of the hemispherical backscattering coefficient of the aerosol to the gas to obtain the integral intensity of the gas hemispherical backscattering signal;

d) Combined with the known scattering phase function of the gas under the surface pressure, the signal intensity of the gas varies with the scattering angle I _air (θ), and the variation of the scattered light signal intensity of the atmosphere with the scattering angle I(θ) is related to that of the gas The difference of signal intensity with the change of scattering angle I _air (θ) is the change of aerosol signal intensity with scattering angle I _aero (θ).

8) The signal intensity of the aerosol varies with the scattering angle I _aero (θ) and the scattering function β _aero (θ) of the aerosol satisfies:

I _aero (θ)＝N ₀ β _aero (θ)

Among them, N ₀ is a constant value for the system parameters, β _aero (θ) is the corresponding scattering function at the scattering angle θ, β _aero (θ) is proportional to I _aero (θ), and the phase function of the aerosol is normalized The distribution of the final scattering function with the angle, so the phase function of the aerosol can be obtained after normalizing I _aero (θ), and the signal intensity of the aerosol is normalized with the change of the scattering angle I _aero (θ), to obtain Aerosol phase function.

Finally, it should be noted that the purpose of announcing the embodiments is to help further understand the utility model, but those skilled in the art can understand that various replacements and Modifications are possible. Therefore, the utility model should not be limited to the content disclosed in the embodiments, and the protection scope of the utility model is subject to the scope defined in the claims.

Claims (2)

1. An aerosol phase function observation system is characterized in that, the aerosol phase function observation system comprises: a laser emission unit, an optical trap, a turbidimeter, a scattering signal receiver and a computer; wherein the laser emission unit A continuous laser beam is emitted in the horizontal direction; an optical trap is installed at the end of the laser beam to absorb the remaining laser light; a turbidity meter is installed below the laser beam, and the air inlet of the turbidity meter is aligned with the laser beam; beside the laser beam and connected to the A scattered signal receiver is installed at the same position as the laser beam; the scattered signal receiver includes a wide-angle lens, a laser filter and a CCD camera. After the film is filtered, it is received by the CCD camera; the turbidimeter and the CCD camera are respectively connected to the computer. 2. the aerosol phase function observation system as claimed in claim 1, is characterized in that, described laser emission unit comprises solid-state laser device and frequency doubling crystal; Described solid-state laser device adopts solid-state laser material as light-emitting substance, and the laser light that sends passes through doubled After the frequency crystal, it becomes a frequency-doubled laser.