An atmospheric fog droplet forward scattering characteristic detection device

Abstract

The utility model discloses an atmospheric mist drop forward scattering characteristic detection device, emit light source unit and the correction unit, detection window, forward scattering detection unit that set gradually along the light path of emitting light source unit emit, and forward heat removal unit includes spatial filter wheel, and the second reflector of oblique setting is fixedly connected on spatial filter wheel, and the second reflector is used for separating transmission light and mist drop forward scattering light. In the utility model, through setting spatial filter wheel at this detection end of forward scattering detection unit, and setting the reflector of inclination, can separate transmission laser beam and scattered light, avoids the detection of scattered light.

Description

Technical Field

[0001] This utility model relates to the field of laser detection technology, and more specifically to a device for detecting the forward scattering characteristics of atmospheric fog droplets. Background Technology

[0002] Fog is a natural weather phenomenon caused by the condensation of water vapor in the atmosphere into tiny water droplets suspended in the air, leading to reduced visibility. Fog droplets are small water droplets that make up fog, with an average diameter ranging from 2 to 20 μm. The number concentration spectrum is commonly used to characterize the distribution of the number of particles of different sizes per unit volume, often referred to as the spectral distribution. This distribution determines the physical and optical properties of the fog droplet swarm, which further influence the atmospheric environment. Fog droplet spectral distributions also exhibit different characteristics in spatial distribution, which, combined with corresponding regional conditions, allows for in-depth regional meteorological research. Furthermore, by observing the temporal dimension of the particle spectrum, the formation, growth, and dissipation processes of atmospheric fog droplets can be obtained, contributing to discussions on climate change. Therefore, accurate measurement of the fog droplet spectrum is a crucial foundation for understanding the physicochemical changes in the atmosphere and revealing the mechanisms of fog formation and dissipation.

[0003] Traditional fog measurement methods employ three-way droplet spectrometers based on inertial trapping principles. However, these methods suffer from drawbacks such as low temporal resolution and limited sample size, making it difficult to record detailed data on fog formation, development, and dissipation in a timely and accurate manner. The development of advanced laser measurement and photoelectric detection technologies has provided technical means for the precise measurement of microscopic particles. Optical measurement methods utilize light beams as experimental probes, including high-speed photography, holography, laser diffraction, and light scattering-based techniques. These methods are suitable for measuring large numbers of fog droplets, offer high precision, and enable online measurement. While image measurement and laser diffraction methods typically require sophisticated optical systems and data analysis algorithms, Mie scattering-based cloud and fog particle measurement techniques are becoming increasingly mature. They offer advantages such as direct measurement, simple structure, and ease of long-term field application. Currently, various cloud and fog detection devices based on different scattering methods are already in operational use.

[0004] According to the Mie scattering theory, the intensity of scattered light from fog droplets within a small forward angle range is sensitive to changes in particle size distribution. The core of atmospheric fog droplet spectrum detection lies in measuring the intensity of scattered light from fog droplets within a specific forward angle range (3°-12°), thereby revealing the size and size distribution of fog droplets.

[0005] Patent document CN102175591A discloses a laser forward-scattering droplet spectral detection system. A red glass mask attached to a window mirror is used to absorb transmitted light, but it cannot completely absorb the transmitted light; the unabsorbed transmitted light affects the detection of scattered light. Furthermore, this patent assumes the laser beam is uniform, but typical laser beams do not meet this requirement (e.g., Gaussian beams). Therefore, the method of introducing a single slit aperture cannot provide a reliable determination of the complete spatial location of the scattered droplets. Utility Model Content

[0006] The technical problem to be solved by this invention is how to improve the detection quality of the detection device.

[0007] This utility model solves the above-mentioned technical problems through the following technical means: an atmospheric fog droplet forward scattering characteristic detection device, an emission light source unit and a correction unit, a detection window and a forward scattering detection unit arranged sequentially along the emission light path of the emission light source unit, the forward heat dissipation unit includes a spatial filter wheel, and a second reflector is fixedly connected to the spatial filter wheel at an angle, the second reflector being used to separate the transmitted light and the fog droplet forward scattering light.

[0008] As a preferred technical solution, the forward heat dissipation unit also includes a focusing lens group, a tilted beam splitter, a second photodetector, and a third photodetector. The focusing lens group, the beam splitter, and the spatial filter wheel are located in the same outgoing light path. The forward scattered light from the droplets is equally divided by the beam splitter and projected onto the second and third photodetectors respectively. The front end of the third photodetector is also provided with a circular aperture.

[0009] As a preferred technical solution, the correction unit includes a first reflecting mirror, a first aperture, a focusing lens, and a second aperture arranged sequentially along the output optical path of the semiconductor laser.

[0010] As a preferred technical solution, the detection window includes a sampling tube, and the sampling tube has detection windows at both ends in the direction of the detection laser beam transmission, and optical windows are fixedly connected to each detection window.

[0011] As a preferred technical solution, the outgoing scattered light collection angle of the space filter wheel is 3°-12°.

[0012] As a preferred technical solution, a connecting piece is fixedly connected to the center of the spatial filter wheel, and the spatial filter wheel is fixedly connected to the connecting piece through multiple connecting blocks, which are distributed at equal angles along the circumference of the connecting piece.

[0013] As a preferred technical solution, the tilt angle of the beam splitter is 45°.

[0014] As a preferred technical solution, the forward heat dissipation unit also includes a photodetector, which is disposed on the optical path after the transmitted light is vertically reflected.

[0015] As a preferred technical solution, the angle between the second reflector and the spatial filter wheel is 45°.

[0016] As a preferred technical solution, the emitting light source unit includes a semiconductor laser with a wavelength of 640nm.

[0017] The beneficial effects of this utility model are as follows:

[0018] (1) In this utility model, by setting a spatial filter wheel and an inclined reflector at the detection end of the forward scattering detection unit, the transmitted laser beam and the scattered light can be separated, which improves the effectiveness of collecting the scattered light signal of the fog droplets and limits the scattered light collection angle to 3°-12°, which further improves the effectiveness of collecting the scattered light signal of the fog droplets.

[0019] (2) In this utility model, the detection of a pair of separate laser beams by a photodetector also provides a basis for correcting the drift of the laser output power during long-term operation of the instrument.

[0020] (3) In this utility model, in order to meet the consistency requirements of the scattering signal of the droplet spectrum detection, on the one hand, the focal point and depth of field of the optical focusing lens group for collecting scattered light are limited to a small, relatively uniform area near the focal point of the laser beam, which serves as the detection area; on the other hand, by setting a circular aperture in front of the third detector, the scattered light in front of, behind and along the edge of the beam collected by the optical focusing lens group is spatially filtered, so that the scattered light of the droplets in the detection area can pass through completely and reach the third photodetector, while the scattered light of the droplets outside the detection area is effectively suppressed, thereby obtaining a reliable basis for judging the consistency of the detection signal of the second photodetector.

[0021] (4) In this utility model, by setting the first aperture, the laser beam is spatially filtered to suppress stray light and improve the beam quality. By setting the second aperture, the stray light backscattered by the sampling tube can be suppressed, stray light is prevented from being reflected multiple times in the optical path, and the signal-to-noise ratio of the forward scattered light signal of the fog droplets can be improved. Attached Figure Description

[0022] Figure 1 A schematic diagram of the overall structure of the atmospheric droplet forward scattering characteristic detection device provided in this embodiment of the utility model;

[0023] Figure 2 This is a schematic diagram of the spatial filter wheel structure provided in an embodiment of the present utility model;

[0024] Reference numerals: 1. Semiconductor laser; 2. First reflecting mirror; 3. First aperture; 4. Focusing lens; 5. Second aperture; 6. First quartz optical window; 7. Second quartz optical window; 8. Sampling tube; 9. Photodetector I; 10. Spatial filter wheel; 11. Second reflecting mirror; 12. Focusing lens group; 13. Beam splitter; 14. Photodetector II; 15. Circular pinhole aperture; 16. Photodetector III. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0026] See Figure 1 A device for detecting the forward scattering characteristics of atmospheric fog droplets includes an emission light source unit and a correction unit, a detection window, and a forward scattering detection unit arranged sequentially along the emission light source unit's output optical path. The emission light source unit includes a semiconductor laser 1. In this embodiment, a semiconductor laser 1 with a wavelength of 640nm is used as the light source. The correction unit includes a first reflecting mirror 2, a first aperture 3, a focusing lens 4, and a second aperture 5 arranged sequentially along the output optical path of the semiconductor laser 1. The emitted laser is reflected by the first reflecting mirror 2 and then spatially filtered by the first aperture 3. The first aperture 3 suppresses stray light emitted by the laser and makes the beam closer to a circular beam. The beam passing through the first aperture 3 is focused by the focusing lens 4. The laser beam focused by the focusing lens 4 enters the detection window through the second aperture 5. The second aperture 5 is used to suppress stray light backscattered by the sampling tube 8.

[0027] The detection window includes a sampling tube 8, which has an axial flow channel. By inputting an atmospheric sample into the sampling tube 8, continuous sampling can be achieved. The sampling tube 8 has detection windows at both ends in the direction of the detection laser beam transmission. In this embodiment, the detection windows are circular. Optical windows are fixedly connected to both detection windows. In this embodiment, the two optical windows are a first quartz optical window 6 and a second quartz optical window 7. The first quartz optical window 6 is located between the second aperture 5 and the left end of the sampling tube 8, and the second quartz optical window 7 is located between the sampling tube 8 and the forward scattering detection unit.

[0028] The laser beam enters the sampling tube 8 after passing through the first quartz optical window 6. The focal point of the laser beam is located at the center of the sampling tube 8. When the laser beam passes through the sampling tube 8, it interacts with the fog droplets in the sampling atmosphere. Some of the light is scattered by the fog droplets. The laser beam and the forward scattered light exit the sampling tube 8 through the second quartz optical window 7.

[0029] See Figure 1 , Figure 2 The forward scattering detection unit includes photodetector 19, spatial filter wheel 10, second reflector 11, focusing lens group 12, beam splitter 13, photodetector 214, circular pinhole aperture 15, and photodetector 316. The spatial filter wheel 10, second reflector 11, focusing lens group 12, and beam splitter 13 are arranged sequentially along the optical path. The spatial filter wheel 10 limits the scattering and collection angle of the emitted scattered light to the range of 3°-12°. A connecting piece is provided at the center of the spatial filter wheel 10. The spatial filter wheel 10 is fixedly connected to the connecting piece by multiple connecting blocks. In this embodiment, three connecting blocks are used as an example, and the three connecting blocks are distributed at equal angles along the circumference of the connecting piece.

[0030] A second reflector 11 is fixedly connected to the center of the spatial filter wheel 10. The second reflector 11 is used to separate the transmitted light from the heat dissipation light. The second reflector 11 is tilted at an angle of 45°, so the transmitted light is reflected vertically. The photodetector 9 is placed on the optical path after the transmitted light is reflected vertically. After photoelectric conversion, the photodetector 9 is used to monitor the power of the detected laser.

[0031] See Figure 1The focusing lens group 12 includes two plano-convex lenses arranged opposite each other. These lenses collect and focus the forward scattered light from the droplets at angles of 3° to 12° after passing through the spatial filter wheel 10. A beam splitter 13 divides the collected forward scattered light into two equal paths. One path is directly focused onto photodetector 14, whose output electrical signal is proportional to the total scattered light intensity and serves as the detection signal. The other path passes through a circular aperture 15 and is focused onto photodetector 16, serving as the discrimination signal. Because the laser beam is scattered by the droplets throughout its transmission path, the intensity of the scattered light before, after, and at the beam edge differs from that at the center of the beam waist, where energy distribution is uniform. This introduces a significant error into the droplet spectrum detection based on scattering intensity. In this embodiment, on the one hand, the focal point and depth of field of the scattered light collecting optical focusing lens group 12 are limited to a small, relatively uniform area near the focal point of the laser beam, which serves as the detection area. On the other hand, when the scattered light from the droplets in front of, behind, and at the edge of the detection area reaches the detector 16 after passing through the optical focusing lens group 12, its focal point will be diffused and laterally shifted relative to the focal point of the scattered light from the droplets in the detection area. By setting a circular aperture stop 15 in front of the detector 16, the scattered light from the front of, behind, and at the edge of the beam collected by the optical focusing lens group 12 in the detection area is spatially filtered, so that the scattered light from the droplets in the detection area can pass through completely, while the scattered light from the droplets outside the detection area is effectively suppressed. This results in the pulse photoelectric signal amplitudes obtained by the forward scattered light from the droplets in the detection area on the photodetector 14 and the photodetector 16 being basically the same, while the scattered light from the droplets outside the detection area is detected by the photodetector 14. The amplitude of the pulsed photoelectric signal obtained from photodetector 316 differs significantly from that of the pulsed photoelectric signal obtained from photodetector 214. By comparing the amplitude of the pulsed droplet scattering detection signal from photodetector 214 and the pulsed droplet scattering discrimination signal from photodetector 316, the validity of the pulsed droplet scattering signal from photodetector 214 can be identified. Only when the amplitudes of the two detection signals are basically the same will they be judged as valid detection signals, thus ensuring the consistency of the droplet scattering signals by particle size. The laser power signal obtained from photodetector 19 is used to normalize the pulsed droplet scattering signal from photodetector 214. The normalized pulsed droplet scattering signal from photodetector 214 is then calibrated using the corresponding scattering intensity calibration signals for different particle sizes. This allows for the measurement of the droplet size passing through the effective detection area. By counting the droplet size over a continuous time period, atmospheric droplet scattering spectrum data can be obtained.

[0032] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A device for detecting the forward scattering characteristics of atmospheric fog droplets, characterized in that, The system includes an emission light source unit and a correction unit, a detection window, and a forward scattering detection unit arranged sequentially along the light path emitted from the emission light source unit. The forward heat dissipation unit includes a spatial filter wheel, on which a second reflector is fixedly connected at an angle. The second reflector is used to separate the transmitted light and the forward scattering light from the fog droplets.

2. The atmospheric fog droplet forward scattering characteristic detection device according to claim 1, characterized in that, The forward heat dissipation unit also includes a focusing lens group, a tilted beam splitter, photodetector two, and photodetector three. The focusing lens group, beam splitter, and spatial filter wheel are located in the same outgoing light path. The forward scattered light from the droplets is equally divided by the beam splitter and directed onto photodetector two and photodetector three respectively. A circular aperture is also provided at the front end of photodetector three.

3. The atmospheric droplet forward scattering characteristic detection device according to claim 1, characterized in that, The correction unit includes a first reflecting mirror, a first aperture, a focusing lens, and a second aperture arranged sequentially along the output optical path of the semiconductor laser.

4. The atmospheric fog droplet forward scattering characteristic detection device according to claim 1, characterized in that, The detection window includes a sampling tube, which has detection windows at both ends in the direction of the detection laser beam transmission, and optical plates are fixedly connected to each detection window.

5. The atmospheric droplet forward scattering characteristic detection device according to claim 1, characterized in that, The outgoing scattered light collection angle of the spatial filter wheel is 3°-12°.

6. The atmospheric droplet forward scattering characteristic detection device according to claim 1, characterized in that, A connecting piece is fixedly connected to the center of the spatial filter wheel. The spatial filter wheel is fixedly connected to the connecting piece through multiple connecting blocks, which are distributed at equal angles along the circumference of the connecting piece.

7. The atmospheric fog droplet forward scattering characteristic detection device according to claim 1, characterized in that, The tilt angle of the beam splitter is 45°.

8. The atmospheric droplet forward scattering characteristic detection device according to claim 1, characterized in that, The forward heat dissipation unit also includes a photodetector, which is positioned on the optical path after the transmitted light is vertically reflected.

9. The atmospheric fog droplet forward scattering characteristic detection device according to claim 1, characterized in that, The angle between the second reflector and the spatial filter wheel is 45°.

10. The atmospheric droplet forward scattering characteristic detection device according to claim 1, characterized in that, The emission source unit includes a semiconductor laser with a wavelength of 640nm.

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