CN106970046A - Cloud particle detection system and method based on Polarization Detection - Google Patents

Abstract

The invention discloses a cloud particle detection system and method based on polarization detection. The system includes a laser emission optical unit generating polarized light, a forward scattering detection unit and a back scattering detection unit; wherein, the laser emission optical unit uses a laser diode, Polarizer and half-wave plate to generate polarized light; through the forward scattering detection unit to determine whether the particle is recorded and get the size of the cloud particle; through the back scattering detection unit to obtain the degree of depolarization of the scattered light to determine the phase state of the particle . The method of the present invention determines the particle size and phase state and other information jointly by the forward scattering detection unit and the back scattering detection unit, and obtains the particle size spectrum distribution of cloud droplets and ice crystals, and then obtains the solid water content and liquid water content in the cloud .

Description

Cloud Particle Detection System and Method Based on Polarization Detection

technical field

The invention relates to a cloud particle detection system and method based on polarization detection, in particular to a cloud particle detection system and method based on continuous light semiconductor lasers, scattering multi-angle reception, and polarization detection, and belongs to the technical field of cloud particle detection.

Background technique

The size spectrum information of small ice crystals in clouds plays an important role in the scientific research of cloud radiology and cloud physics. The Fifth Assessment Report of the IPCC pointed out that there are still great uncertainties in the role of clouds in radiative forcing and climate change, and an important source of uncertainty is caused by cold cloud radiation. The radiation characteristics of cold clouds depend not only on the ice water content, but also on its shape and scale spectrum distribution information. In order to deeply understand its radiation transfer characteristics, the ice crystal information in the cloud is an essential physical parameter, especially for the ice crystals in the cloud. The recognition of the majority of ice crystal particles smaller than 50 μm is particularly important. In the study of cloud physics, cold clouds are also the main object of artificial weather modification and play an important role in the formation of precipitation. Small ice crystals play an important role in the formation of convective cloud ice crystals. Ice crystals in clouds directly affect the formation of precipitation no matter in the process of cold cloud hydrostatic catalysis or cumulus dynamic catalysis. Modern cloud particle detection technology has promoted a further understanding of cloud physical processes. However, the understanding of the process from small ice crystals (supercooled water) to the microphysics of precipitation is not very clear. Model research on this process requires a large amount of experimental data as support and verification. The development and change of ice cores can be studied in a wide time scale (several hours) by using ground cloud chambers, but modern observations require time scales on the order of minutes, so cloud chamber simulations cannot be completed, and the environment of cloud chambers is inevitably related to the natural environment There is a certain difference. Airborne cloud particle observation is another important means of cloud physics research. Since the first airborne ice crystal collection experiment was carried out in the 1940s, airborne observation has deepened people's understanding of cloud physics science. But so far there is no relevant airborne instrument that can observe and record the occurrence and development process of ice crystals in cold clouds, which leads to great difficulties in understanding the formation process of precipitation in cold clouds. If we can observe the early formation process of ice crystals in clouds, it will break through our understanding of the formation process of ice crystals in mixed clouds, which will help in-depth understanding of the microphysical change process and mechanism in clouds. In conclusion, the information of ice crystals in cold clouds is very important to the study of cloud radiation and cloud physics, but due to the lack of corresponding airborne detection instruments, it is necessary to carry out research on the detection principles and methods of small ice crystals in cold clouds. The small ice crystal detector is carried to realize the effective detection of small ice crystals in cold clouds, and solve the current problems in the understanding of ice crystals in cloud radiation and cloud physics.

At present, the most widely used airborne instruments for cloud microphysical characteristics observation are mainly based on single particle scattering technology and imaging technology. Among them, the cloud particles within 50 μm are mainly measured by the scattering method. This method collects the scattered light energy of the cloud particles in a certain spatial solid angle, and calculates the optical equivalent particle size of the cloud particles according to the calibration results and the scattering principle of spherical particles. This method is based on the Mie scattering principle of spherical particles, and only detects the scattered energy information, and does not have the ability to distinguish liquid water from ice crystals, which produces a large error in the measurement of ice crystals. The two-dimensional particle probe based on imaging technology uses a linear array detector to obtain the projection of each particle when it passes through the laser beam. Considering the error caused by the detector's spatial resolution and AD conversion, the lower limit of the instrument's detection of cloud particles is 100 μm. It is also impossible to realize the observation of small-sized ice crystals. Baumgardner reported an improved scattering cloud particle detector in 2001. The system receives backscattering while receiving forward scattering of cloud particles, and judges the phase state of cloud particles according to the ratio of forward scattering and backscattering. The oscillation of meter scattering leads to the oscillation of the forward-backward ratio, which affects the accuracy of particle phase state judgment. Lawson reported a high-resolution cloud particle imaging system in 2001. The system uses a laser with a pulse of 20 ns to irradiate cloud particles, and uses a CCD to record cloud particle imaging. Insufficient to record the distribution of small ice crystals in clouds. Fugal established a holographic imaging system for online cloud particle measurement in 2004. Due to the limitation of CCD response speed, the noise caused by the imaginary part of the light field during the interference process, and the complex holographic imaging algorithm, the system can be used when the cloud particle number concentration is large. Large measurement errors occur. Hirst reported the Small Ice Detector (SID: Small Ice Detector) based on scattering stripes in 2001. The shape of the scattering stripes of ice crystals is very different from that of cloud droplet Airy stripes. Based on this, the phase state of cloud particles can be judged. The first generation of SID Using a line array of 6 detectors, the angular resolution is limited. Cotton reported in 2010 that the second-generation ice crystal detector SID-2 uses custom-made concentric circle-distributed phase function detectors (32 detectors), and the sensitivity of the detector has also been greatly improved, but when the cloud particle concentration exceeds 20 /cm ³ , SID-2 cannot distinguish individual particles. The third-generation SID-3 uses a high-resolution camera to perform two-dimensional imaging of the fringes to obtain high angular resolution. However, due to the slow processing speed of the camera, when the concentration of ice crystal particles is large, particle degeneracy occurs. The actual measurement The number of particles is smaller than the actual particle book. Since the phase state discrimination method based on shape detection is limited by particle degeneracy, scientists have turned to the use of polarization techniques to distinguish particle phase states in recent years.

Based on the development of cloud particle detectors at home and abroad, the current small ice crystal detection technologies mainly include scattering ratio measurement, holographic imaging, and scattering fringe imaging. The scattering ratio measurement method is limited by the oscillation of the Mie scattering phase function, and the imaging technology will produce degeneracy when there are many ice crystal particles due to the response of the imaging detector. The detection of small ice crystals based on polarization detection is rarely studied. Therefore, the detection of small ice crystals (less than 50 μm) in ice clouds or mixed-phase clouds is still an unsolved problem.

Contents of the invention

The technical problem to be solved by the present invention is: provide a cloud particle detection system and method based on polarization detection, use cloud particles to depolarize the laser to distinguish particle phase states, establish a cloud particle detection system based on polarization detection, and realize the detection of cloud droplets and ice crystals Quantitative detection of phase separation.

The present invention adopts the following technical solutions for solving the problems of the technologies described above:

The cloud particle detection system based on polarization detection includes a laser emission optical unit that generates polarized light, a forward scattering detection unit, a backscatter detection unit, a four-channel acquisition card, and a data processing unit; wherein the laser emission optical unit includes a laser, a polarization plate, half-wave plate and the first total reflection mirror; the forward scatter detection unit includes the second total reflection mirror sealed inside the first glass container, the laser energy monitor, the forward scattered light collection lens, the narrow band filter, the first Three total reflection mirrors, a first converging lens, a beam splitting prism, a first photodetector, an aperture diaphragm and a second photodetector, the first glass container includes a first window glass; the backscatter detection unit includes a sealed second photodetector. The first backscattered light collecting lens, the second converging lens, the second backscattering light collecting lens, the polarizing beam splitting prism, the third converging lens, the parallel polarized detector, the fourth converging lens, the vertical polarized a detector, the second glass container including a second window glass;

The laser light emitted by the laser device passes through the polarizer and the half-wave plate to reach the first total reflection mirror in turn, and the first total reflection mirror reflects the laser light to the center position of the first window glass and the second window glass, and generates forward scattered light and backscattered light;

After the forward scattered light passes through the first window glass, part of it is transmitted to the laser energy monitor through the second total reflection mirror for energy monitoring, and the other part is collected by the forward scattered light collecting lens, and passed through the narrow-band filter and then transmitted to the laser energy monitor for energy monitoring. The three full mirrors introduce the first converging lens for convergence, and the converged scattered light is divided into 3:1 by the beam splitting prism, of which 25% enters the first photodetector, and 75% enters the second photodetector through the aperture diaphragm ;

After the backscattered light passes through the second window glass, it is collected by the first backscattered light collecting lens, and after passing through the telescope formed by the second converging lens and the second backscattered light collecting lens, it is divided into Parallel polarized light and vertically polarized light, the parallel polarized light is detected by the parallel polarized detector after passing through the third converging lens, and the vertically polarized light is detected by the vertical polarized detector after passing through the fourth converging lens;

The first photodetector, the second photodetector, the parallel polarization detector, and the vertical polarization detector are respectively connected to a four-channel acquisition card, and the four-channel acquisition card is connected to a data processing unit.

As a preferred solution of the present invention, both the first window glass and the second window glass are quartz plates.

As a preferred solution of the present invention, the laser has a wavelength of 660nm and an output power of 120mW.

As a preferred solution of the present invention, the receiving solid angle formed by the forward scattered light collecting lens is 4-14°, and the receiving solid angle formed by the first back scattered light collecting lens is 146-176°.

As a preferred solution of the present invention, the central transmission wavelength of the narrow-band filter is 660 nm, the bandwidth is 10 nm, and the transmittance within the bandwidth is 90%.

As a preferred solution of the present invention, the first total reflection mirror, the second total reflection mirror and the third total reflection mirror are all 660nm 45° total reflections.

As a preferred solution of the present invention, the size of the aperture diaphragm is 200 μm*200 μm.

The cloud particle detection method based on polarization detection comprises the following steps:

Step 1, the laser outputs laser light, which passes through the polarizer and the half-wave plate in turn to the first total reflection mirror, and the first total reflection mirror reflects the laser light to the center of the measurement area, that is, the first window glass and the second window glass, generating a forward direction scattered light and backscattered light;

Step 2, after the forward scattered light passes through the first window glass, part of it is transmitted to the laser energy monitor by the second total reflection mirror for energy monitoring, and the other part is collected by the forward scattered light collection lens, and passed through the narrow-band filter by the The third total reflection mirror introduces the first converging lens for convergence, and the converged scattered light is divided into 3:1 by the beam splitting prism, of which 25% enters the first photodetector, and 75% enters the second photodetector through the aperture diaphragm device;

Step 3: After the backscattered light passes through the second window glass, it is collected by the first backscattered light collecting lens, and after passing through the telescope formed by the second converging lens and the second backscattered light collecting lens, it is split by the polarization beam splitter prism. It is parallel polarized light and vertically polarized light, the parallel polarized light is detected by the parallel polarized detector after passing through the third converging lens, and the vertically polarized light is detected by the vertical polarized detector after passing through the fourth converging lens;

Step 4, use the four-channel acquisition card to collect the electrical signals detected by each detector, and judge whether the second photodetector detects the electrical signal, if so, enter step 5, otherwise, return to step 1;

Step 5: Calculate the depolarization of cloud particles according to the detection results of the parallel polarization detector and the vertical polarization detector, and compare it with the preset threshold value. If it is greater than or equal to the preset threshold value, it is judged as an ice crystal, and the number of ice crystals is increased by one , if it is less than the preset threshold, it is judged as liquid water, and the number of cloud droplets is increased by one.

Compared with the prior art, the present invention adopts the above technical scheme and has the following technical effects:

1. The present invention uses the depolarization of particles to determine the particle phase state. Compared with traditional cloud particle detectors, the polarization factor is added. The cloud particle detection system established has the ability to distinguish cloud droplets and ice crystals, and modern laser technology and detection Technology provides the feasibility of the present invention. At present, the polarization purity of the polarization laser can reach 100:1, and the isolation of the polarization beam splitter can reach 1000:1, which provide convenience for polarization detection.

2. The present invention comprehensively utilizes the measured forward scattering and depolarization results to obtain the particle size distribution of cloud droplets and ice crystals, thereby obtaining the solid water content and liquid water content in the cloud, and realizes the quantitative detection of the phase separation of cloud droplets and ice crystals.

Description of drawings

Fig. 1 is a schematic diagram of the optical path of the cloud particle detection system based on polarization detection according to the present invention.

Fig. 2 is a flow chart of the cloud particle detection method based on polarization detection in the present invention.

Fig. 3 is the response curve of the existing forward scattering airborne cloud particle detector to the liquid droplet.

Figure 4 shows the relationship between the depolarization and scattering angle of non-spherical particles and spherical particles with an equivalent particle radius of 0.5 microns and an aspect ratio of 2.

Figure 5 shows the relationship between depolarization and aspect ratio of particles of different shapes in the backscattering direction when the particle equivalent radius is 0.5 microns.

Among them, 1-laser, 2-polarizer, 3-half-wave plate, 4-the first total reflection mirror, 5-the first window glass, 6-the second total reflection mirror, 7-laser energy monitor, 8-front Scattered light collecting lens, 9-narrow band filter, 10-third total reflection mirror, 11-first converging lens, 12-beam splitting prism, 13-first photodetector, 14-aperture diaphragm, 15 - second photodetector, 16 - second window glass, 17 - first backscattered light collecting lens, 18 - second converging lens, 19 - second backscattered light collecting lens, 20 - polarizing beam splitting prism, 21-third converging lens, 22-parallel polarization detector, 23-fourth converging lens, 24-perpendicular polarization detector.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

The cloud particle detection system and method based on polarization detection of the present invention realizes the quantitative detection of cloud droplets and ice crystal phase separation. The system includes a laser emitting optical unit for generating polarized light, a forward scattering detection unit, a back scattering detection unit, four The channel acquisition card and data processing unit are shown in Figure 1 and Figure 2, and the four-channel acquisition card and data processing unit are not shown in the figure.

The laser emitting optical unit includes: a photodiode high-power laser 1 , a polarizer 2 , a half-wave plate 3 and a first total reflection mirror 4 .

The forward scatter detection unit includes: a first window glass 5, a second total reflection mirror 6, a laser energy monitor 7, a forward scattered light collection lens 8, a narrow band filter 9, a third total reflection mirror 10, a first converging A lens 11 , a beam splitting prism 12 , a first photodetector 13 , an aperture stop 14 and a second photodetector 15 .

The backscatter detection unit includes: a second window glass 16, a first backscattered light collecting lens 17, a second converging lens 18, a second backscattering light collecting lens 19, a polarizing beam splitting prism 20, and a third converging lens 21 , a parallel polarization detector 22 , a fourth converging lens 23 , and a vertical polarization detector 24 .

The laser light emitted by the photodiode high-power laser 1 can compress the vertical component of the laser light by rotating the polarizer 2 to make the transmission direction parallel to the polarization direction of the laser, so as to obtain more pure polarized light and reduce background noise; the half-wave plate 3 is used By rotating the polarization direction of the laser light, the emitted laser light is matched with the subsequent polarization beam splitter prism 20, so that the emitted laser light can pass through the polarization beam splitter prism 20 smoothly, and the backscattered light can enter the respective detectors through the polarization beam splitter prism 20. Parallel polarization detector 22 and vertical polarization detector 24, the first total reflection mirror 4 reflects the laser light to the middle of the measurement area, that is, the center between the first window glass 5 and the second window glass 16 .

The forward scattered light 4-14 ° behind the first window glass 5 is collected by the forward scattered light collecting lens 8, and the forward scattered light of 0-4 ° is transmitted to the laser energy monitor 7 through the second total reflection mirror 6 for further processing. Energy monitoring, the collected forward scattered light is introduced into the first converging lens 11 by the third total reflection mirror 10 after passing through the narrow band filter 9, and the converged scattered light is divided into 3:1 by the energy beam splitting prism 12, 25% of the front Scattered light enters the detection channel photodetector 13 to obtain the size of the particle in combination with the system response curve during calibration. The system response curve is obtained by the following method: select standard glass ball particles of different sizes, and send glass ball particles of the same size into the detection system , multiple glass ball particles are fed each time, and the photodetector of the measurement channel is used to determine the response range of particles of this size. According to the response range, it is transformed into the response range of the system to water according to meter scattering. This part is generally applicable to existing Forward Scatter Cloud Particle Detector.

75% of the forward scattered light enters the quality control channel photodetector 15 through the aperture diaphragm 14 to distinguish the position of the cloud particle to determine whether the particle is recorded. When the particle passes through the center of the measurement area, the light is detected The focus is very small, and it can pass through the small hole smoothly. As the position of the particle entering the optical path deviates from the center, the image becomes larger, causing part of the light to be blocked by the small hole diaphragm. The more the position away from the center, the more light is blocked. The output of the photodetector 15 of the quality control channel and the photodetector 13 of the detection channel becomes 1:1, and the path passed by the particle at this time is the extreme edge of the measurement sensitive area.

The backscattered light 146-176 ° by the second window glass 16 is collected by the first backscattered light collecting lens 17, and is polarized by the telescope system formed by the second converging lens 18 and the second backscattered light collecting lens 19 The beam splitting prism 20 separates the parallel polarization and the vertical polarization, and after being converged by the third converging lens 21 and the fourth converging lens 23 respectively, it is detected by the parallel polarization detector 22 and the vertical polarization detector 24 to obtain the parallel polarization component I _// and the vertically polarized component I _⊥ , by the formula Calculate the depolarization, where, with are the background values of parallel polarization and perpendicular polarization under particle-free conditions, respectively.

The scattering characteristics of non-spherical particles are studied by methods such as T-matrix method, finite-difference time-domain method and geometric optics algorithm. The T-matrix method is calculated by the following method: the Stokes vectors of the incident beam and the scattered beam pass through a 4*4 Mueller matrix F, for each scattering angle θ, there is the following relationship:

Among them, I _in , _Qin , U _in and _Vin are the four Stokes parameters of the incident light; I _sc , Q _sc , U _sc and V _sc are the four Stokes parameters of the scattered light; λ is the wavelength; D is The distance from the particle to the detector.

Here, four Stokes parameters I, Q, U, and V are used to describe the polarization state of a beam of light, which are defined as follows:

In the formula, with Indicates the amplitude of the electric field in the x and y directions, and δ _x (t) and δ _y (t) represent the phase in this direction.

The column matrix of the above four parameters as elements represents a four-dimensional parameter called a Stokes vector. [ ^IQUV ] This group of parameters can represent the state of any polarized light including the degree of polarization. I, Q, U, V all have the dimension of light intensity. I-indicates the total light intensity; Q-indicates the linearly polarized light component in the X-axis direction; U-indicates the linearly polarized light component in the 45° direction; V-indicates the right-handed circularly polarized light component.

Vertical linearly polarized light, -45° linearly polarized light, and left-handed circularly polarized light, which are orthogonal to the above polarization states, are represented by negative values of Q, U, and V.

When the laser polarization direction is parallel to the scattering section, the parallel and perpendicular components of the scattered light can be written as:

When the laser polarization direction is perpendicular to the scattering section, the parallel and perpendicular components of the scattered light can be written as:

Stokes parameters of parallel polarized incident light: Q _in =I _in , U _in =V _in =0;

Stokes parameters of vertically polarized incident light: Q _in =-I _in , U _in =V _in =0;

Then the Stokes parameter of the scattered light can be obtained by multiplying the Stokes parameter of the incident light by the Mueller matrix:

The Stokes parameter of the scattered light of the parallel polarized incident light is expressed as:

The Stokes parameter of scattered light for vertically polarized incident light is expressed as:

The relationship between the wave number k and the wavelength λ can be obtained by the formula For conversion, there is F ₂₁ =F ₁₂ for any particle direction.

The linear depolarization ratio for scattered light with parallel polarized incident light can be written as:

The linear depolarization ratio of scattered light for perpendicularly polarized incident light can be written as:

Through the above method, the particles of different shapes and sizes are calculated to obtain their depolarization, and the polarization characteristic database is established for different particle models.

Figure 4 shows the relationship between the depolarization and scattering angle of non-spherical particles and spherical particles with an equivalent radius of 0.5 μm and an aspect ratio of 2 calculated by the T-matrix method. Among them, the depolarization ratio of spherical particles is 10 orders of magnitude smaller than that of ellipsoidal particles and cylindrical particles. Calculate the average of the depolarization of the backscattering angle 146°-176° of these three kinds of particles, and the depolarization of the ellipsoidal particle is 0.227, the depolarization of the cylindrical particle is 0.207, and the equivalent radius is 0.5 microns The depolarization of spherical particles is 2.51*10 ^-11 , which is almost close to 0. A threshold can be obtained to distinguish spherical particles from non-spherical particles. Considering the different depolarizations of various sizes and shapes, and in order to reduce judgments, the present invention uses The depolarization ratio of 0.01 is the threshold value, and the threshold value is less than the threshold, which is liquid spherical particles, and the threshold value is greater than or equal to the threshold value, which is solid particles.

Figure 5 shows the relationship between the depolarization of particles with different shapes and their aspect ratios in the backscattering direction when the particle equivalent radius calculated by the T-matrix method is 0.5 microns. When approaching, the depolarization value is also approaching 0, but because the solid angle range we receive is larger, the distinction between solid and liquid can also be guaranteed.

The system collects the scattering signal information of each cloud particle, and compares the depolarization obtained by the backscattering module with the depolarization threshold. When it is greater than or equal to the depolarization threshold, it is a non-spherical particle, that is, an ice crystal particle; Judgment is liquid.

The system receives the scattering of cloud particles in two directions, and collects forward scattering and back scattering respectively. signal, the size and phase of the particle under test can be inferred.

The optical path of the cloud particle detection system based on polarization detection includes the following steps:

1) Photodiode high-power laser output laser, the output power is 120mW, and the spot size is 0.5mm;

2) Turn the polarizer to obtain the same pure polarized light as the polarizing beam splitter;

3) Use the 45° first total reflection mirror to reflect the laser light to the measurement sensitive area (the center position between the first window glass and the second window glass);

4) The sensitive area of the system is determined by the depth-of-field limiting aperture. Place the 200μm*200μm small hole in the middle of the sensitive area, and link the detectors of the quality control channel and the measurement channel to the oscilloscope to display their voltage values. A three-dimensional adjustment platform is used to fine-tune the small hole to the position where the voltage of the two channels is the largest. Since the beam splitter prism divides the converged signal into two parts of 3:1, and the transmission is 3 and the reflection is 1, the change of the signal of the quality control channel is greater than that of the detection. The channel signal changes. At this time, the ratio of the two channels is at most 3:1. Record the voltage values of the two channels at this time, until the ratio of the quality control channel to the detection channel is less than 0.5. Likewise, a similar method can be used to measure the effective width of the irradiating laser beam to determine the sampling area of the system;

5) After measuring the sensitive area, the laser direct light is reflected by the 45° second total reflection mirror to the laser energy monitor for monitoring;

6) The forward scattering receiving device is isolated from the outside air through the window glass;

7) The forward scattering lens collects the scattered light signal within 14°;

8) Use a narrow-band filter to suppress the collected stray light and increase the signal-to-noise ratio;

9) Use a total reflection mirror to fully reflect the forward scattered light;

10) The forward scattered light is converged by the converging lens;

11) The beam-splitting prism divides the focused forward scattered light into two parts of 3:1, and the beam-splitting prism transmits 3 and reflects 1;

12) The reflection part of the beam splitting prism corresponds to the quality control channel, a small hole is placed in front of the detector for quality control, and the transmission part is directly detected by the photodetector.

13) The backscattering part of the optical element is isolated from the outside atmosphere through the window glass;

14) The converging lens converges the backscattered light;

15) A group of telescope systems further converge the backscattered light;

16) The polarizing beam splitter divides the focused backscattered light into parallel polarized light and vertical polarized light;

17) The parallel polarized light and the vertically polarized light are respectively detected by the parallel polarization detection channel and the vertical polarization detection channel after being converged by the converging lens;

18) According to the results obtained by the measurement channel, combined with the response curve of the developed forward scattering cloud particle detector to the droplet (as shown in Figure 3), query the scale of the cloud particles;

19) According to the formula Combining the detection results of the parallel polarization channel and the vertical polarization channel to calculate the depolarization of the particle, compare it with the threshold value of 0.01, if it is greater than or equal to the threshold value, it is defined as an ice crystal, and add one to the number of ice crystals, if it is less than the threshold value, judge is liquid water, and add one to the number of cloud droplets;

20) By performing the above processing on each particle scattering signal, the number of particles in different phases per unit time can be obtained. Considering the measurement sensitive area of the system and the flight speed of the aircraft, the particle size distribution of cloud droplets and ice crystals can be obtained. Then the solid water content and liquid water content in the cloud can be obtained.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (8)

1. the cloud particle detection system based on Polarization Detection, it is characterised in that the Laser emission optics list including producing polarised light Member, forward scattering probe unit, backscatter sounding unit, four-way capture card and data processing unit；Wherein, laser is sent out Penetrating optical unit includes laser (1), polarizer (2), half-wave plate (3) and the first total reflective mirror (4)；Forward scattering probe unit bag Include the second total reflective mirror (6) being sealed in inside the first glass container, LASER Energy Monitor (7), forward scattering light collecting lens (8), narrow band pass filter (9), the 3rd total reflective mirror (10), the first convergent lens (11), beam splitter prism (12), the first photodetector (13), aperture (14) and the second photodetector (15), the first glass container include first window glass (5)；It is backward to dissipate Penetrating probe unit includes being sealed in the first rear orientation light collecting lens (17), the second convergent lens inside the second glass container (18), the second rear orientation light collecting lens (19), polarization beam splitter prism (20), the 3rd convergent lens (21), parallel polarization are visited Device (22), the 4th convergent lens (23), vertical polarization detector (24) are surveyed, the second glass container includes the second window glass (16)；

The laser of laser (1) transmitting passes sequentially through polarizer (2), half-wave plate (3) and reaches the first total reflective mirror (4), first Total reflective mirror (4) reflects the laser light to the center of first window glass (5) and the second window glass (16), and produces preceding to scattered Penetrate light and rear orientation light；

After the forward scattering light is by first window glass (5), a part is transmitted to laser energy by the second total reflective mirror (6) supervises Visual organ (7) carry out energy monitoring, another part by forward scattering light collecting lens (8) collect, and after narrow band pass filter (9) by 3rd total reflective mirror (10) introduces the first convergent lens (11) and enters line convergence, and the scattered light of convergence is divided into 3 by beam splitter prism (12):1, Wherein, 25% enters the first photodetector (13), and 75% enters the second photodetector (15) through aperture (14)；

After the rear orientation light is by the second window glass (16), collected by the first rear orientation light collecting lens (17), warp After the telescope that second convergent lens (18) and the second rear orientation light collecting lens (19) are constituted, by polarization beam splitter prism (20) It is divided into parallel polarized light and orthogonal polarized light, parallel polarized light is after the 3rd convergent lens (21) by parallel polarization detector (22) Detected, orthogonal polarized light is detected after the 4th convergent lens (23) by vertical polarization detector (24)；

First photodetector (13), the second photodetector (15), parallel polarization detector (22), vertical polarization detection Device (24) is connected with four-way capture card respectively, and four-way capture card is connected with data processing unit.

2. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that the first window glass Glass (5), the second window glass (16) are quartzy flat board.

3. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that the laser (1) Wavelength is 660nm, and power output is 120mW.

4. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that the forward scattering light The formed solid angle that receives of collecting lens (8) is 4-14 °, and the first rear orientation light collecting lens (17) is formed to receive solid angle For 146-176 °.

5. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that the narrow band pass filter (9) center is 660nm through wavelength, with a width of 10nm, and transmitance is 90% in bandwidth.

6. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that first total reflective mirror (4), the second total reflective mirror (6) and the 3rd total reflective mirror (10) are that 45 ° of 660nm are all-trans.

7. the cloud particle detection system based on Polarization Detection according to claim 1, it is characterised in that the aperture (14) size is 200 μm * 200 μm.

8. the cloud particle detection method based on Polarization Detection, it is characterised in that comprise the following steps：

Step 1, laser (1) output laser, sequentially passes through polarizer (2), half-wave plate (3) and reaches the first total reflective mirror (4), first Total reflective mirror (4) reflects the laser light to the measured zone i.e. center of first window glass (5) and the second window glass (16), production Before death to scattered light and rear orientation light；

Step 2, after forward scattering light is by first window glass (5), a part is transmitted to laser energy by the second total reflective mirror (6) Monitor (7) carries out energy monitoring, and another part is collected by forward scattering light collecting lens (8), and after narrow band pass filter (9) First convergent lens (11) is introduced by the 3rd total reflective mirror (10) and enters line convergence, the scattered light of convergence is divided into 3 by beam splitter prism (12): 1, wherein, 25% enters the first photodetector (13), and 75% enters the second photodetector (15) through aperture (14)；

Step 3, after rear orientation light is by the second window glass (16), collected by the first rear orientation light collecting lens (17), After the telescope constituted through the second convergent lens (18) and the second rear orientation light collecting lens (19), by polarization beam splitter prism (20) it is divided into parallel polarized light and orthogonal polarized light, parallel polarized light is after the 3rd convergent lens (21) by parallel polarization detector (22) detected, orthogonal polarized light is detected after the 4th convergent lens (23) by vertical polarization detector (24)；

Step 4, the electric signal that the detection of each detector is obtained is gathered using four-way capture card, and judges the second photodetector (15) whether electric signal is detected, is then to enter step 5, otherwise, return to step 1；

Step 5, moving back for cloud particle is calculated according to the result of detection of parallel polarization detector (22) and vertical polarization detector (24) Partially, and with predetermined threshold value contrasted, if more than or equal to predetermined threshold value, being judged as ice crystal, and ice crystal number is added one, if small In predetermined threshold value, then it is judged as aqueous water, and water dust number is added one.