Method for reducing blind area of atmospheric laser radar

Abstract

The invention relates to the field of atmospheric parameter detection, in particular to a method for reducing a blind area of an atmospheric laser radar, which comprises the following steps: S1, a transmitting end emits a laser beam through a transmitting control mirror to form a first transmitting view field, and the main axis of the first transmitting view field is parallel to the main axis of a receiving view field of a receiving end; s2, the angle of the emission control mirror is changed, the emission end emits a second emission view field through the emission control mirror, and an angle is formed between the main axis of the second emission view field and the main axis of the receiving view field; and S3, the receiving end transmits the obtained data to a data processing system for processing through photoelectric conversion. The first emission view field sequentially comprises a direct dead zone, a direct transition zone and a direct full zone from near to far; and the second emission view field sequentially comprises a first oblique incidence blind area, a first oblique incidence transition area, an oblique incidence full area, a second oblique incidence transition area and a second oblique incidence blind area from near to far. According to the invention, the blind area of the atmospheric laser radar can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of atmospheric parameter detection, and in particular to a method for reducing the blind area of ​​an atmospheric laser radar. Background Art

[0002] Atmospheric LiDAR is an active remote sensing tool that inverts atmospheric properties by detecting radiation signals from the interaction between lasers and various molecules and atmospheric aerosol particles in the atmosphere. When the laser beam propagates in the atmospheric medium, it undergoes energy conversion with various gas molecules and atmospheric aerosol particles in the atmospheric medium on the propagation path, and then redistributes the energy in different forms according to different conversion mechanisms, so that the particles not only affect the laser radiation, but also attach a lot of information about the physical, chemical and optical characteristics of the particles themselves. This lays a theoretical foundation for LiDAR detection, and is widely used in the detection of atmospheric aerosols, visibility, atmospheric boundary layer, atmospheric pollutants, water vapor, ozone, atmospheric wind field, atmospheric density, atmospheric temperature and atmospheric pressure, etc.

[0003] Since lidar can monitor the spatial distribution of many important atmospheric components and has the advantages of large measurement range and high temporal and spatial resolution, it plays an irreplaceable role that other ground-based means cannot. It will have broader application prospects in the fields of atmosphere, environment, meteorology, remote sensing, and military.

[0004] Blind spots refer to areas that the LiDAR cannot effectively detect or measure. These areas are usually due to the geometric structure of the LiDAR transmitting and receiving modules, which prevents the signal from returning to the receiver. Generally, single-field-of-view reception is adopted. The field of view of the transmitting system and the field of view of the receiving system have different overlapping efficiencies at different distances, thus affecting the reception of the transmitted signal. This is called the "geometric factor" effect. Due to the existence of the "geometric factor" effect, traditional Mie scattering LiDAR has a large blind spot, which usually ranges from tens of meters to hundreds of meters. The echo information near the ground or in the range close to the LiDAR cannot be accurately characterized, and cannot effectively, timely, and quantitatively reflect the distribution information of atmospheric composition and pollutants.

[0005] At present, the following methods are usually used to solve the blind spot problem: (1) Add a set of receiving devices, including a secondary telescope, a receiving optical path and a data acquisition system (Development and Application of Dual-Field Zero Blind Zone Lidar_Wang Jie). This increases the device cost of the atmospheric Lidar, and the zero blind zone radar can only be close to the zero blind zone in theoretical calculations. In fact, there is no atmospheric Lidar with zero blind zone.

[0006] (2) Scanning laser radar, driven by the gimbal, can change the direction of light emission through the whole system. By adjusting the pitch angle from 0 to 90 degrees, the laser covers the observation area from horizontal to vertical. The horizontal observation part is used for low-altitude detection, and the vertical observation part is used for high-altitude detection. Then the blind area is reduced by splicing the data. This method is suitable for laser radar installation in areas with no obstructions on all sides, but the scanning range of 0 to 90 degrees is too large, and it takes too long to obtain a section of spliced ​​data without blind areas, so the detection efficiency is relatively low.

[0007] (3) Based on CCD imaging laser radar, there is no blind spot. Due to the influence of daytime background light, the laser echo signal is submerged in the solar spectrum and the noise is very large. This solution is only suitable for night observation. Summary of the invention

[0008] The invention relates to a method for reducing the blind area of ​​an atmospheric laser radar, which solves the problem that the blind area of ​​an atmospheric laser radar with a single transmitting end is large.

[0009] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: A method for reducing the blind area of ​​an atmospheric laser radar, comprising: S1. The transmitting end emits a laser beam through a transmitting control mirror to form a first transmitting field of view, so that the main axis of the first transmitting field of view is parallel to the main axis of the receiving field of view of the receiving end; S2. Change the angle of the launch control mirror, the launch end emits a laser beam through the launch control mirror to form a second launch field of view, the second launch field of view main axis and the receiving field of view main axis have an angle; S3. The receiving end transmits the acquired data to the data processing system for processing through photoelectric conversion.

[0010] Furthermore, the first transmitting field of view is in a paraxial relationship with the receiving field of view, and the receiving field of view partially overlaps with the first transmitting field of view; and the second transmitting field of view runs through the receiving field of view.

[0011] Furthermore, the first emission field of view is, from near to far, a direct blind zone, a direct transition zone, and a direct full zone; the second emission field of view is, from near to far, a first oblique blind zone, a first oblique transition zone, an oblique full zone, a second oblique transition zone, and a second oblique blind zone.

[0012] Furthermore, the blind area is an area where the transmitting field of view does not intersect with the receiving field of view, the transition area is an area where the transmitting field of view partially intersects with the receiving field of view, and the filled area is an area where the transmitting field of view is included in the receiving field of view.

[0013] Furthermore, the emission control mirror adjusts the tilt angle so that the upper limit of the second oblique transition zone is higher than the lower limit of the vertical transition zone.

[0014] Furthermore, the data obtained by the receiving end in S3 includes high-altitude echo data and low-altitude echo data. The high-altitude echo data uses data obtained from the direct transition zone and the direct full zone, and the low-altitude echo data uses data obtained from the first oblique transition zone, the oblique full zone and the second oblique transition zone. The obtained high-altitude echo data and low-altitude echo data are spliced ​​to reduce the echo data in the blind spot.

[0015] Furthermore, the transmitting end includes a transmitting laser, and the receiving end includes a receiving optical system; the receiving optical system is connected to a receiving electrical system, and the receiving electrical system is connected to a data processing system.

[0016] By adopting the above technical solution, the beneficial technical effects of the present invention are: The present invention proposes a method for splicing the transmission laser detection data parallel to the main axis of the receiving field of view and the tilted transmission laser detection data through a transmission control mirror device to make the atmospheric laser radar observation area overlap with the near-ground point sensor observation area, which will greatly expand its use scenarios and application scope. The present invention can significantly reduce the blind area of ​​the atmospheric laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a method for reducing the blind area of ​​atmospheric lidar.

[0018] Figure 2 Schematic diagram of the transmitting field of view and the receiving field of view.

[0019] Figure 3 This is a schematic diagram showing that the principal axis of the transmitting field of view is parallel to the principal axis of the receiving field of view.

[0020] Figure 4 Schematic diagram showing that the main axis of the transmitting field of view and the main axis of the receiving field of view have an angle. DETAILED DESCRIPTION Example 1

[0021] like Figure 1 As shown, a method for reducing the blind area of ​​an atmospheric laser radar comprises: S1. The transmitting end emits a laser beam through the transmitting control mirror to form a first transmitting field of view 1, and the receiving end forms a receiving field of view, so that the main axis of the first transmitting field of view 1 is parallel to the main axis of the receiving field of view of the receiving end; S2. Change the angle of the launch control mirror, the launch end emits a laser beam through the launch control mirror to form a second launch field of view 3, the second launch field of view 3 main axis and the receiving field of view 2 main axis have an angle; S3. The receiving end transmits the acquired data to the data processing system for processing through photoelectric conversion.

[0022] like Figure 2As shown, the direction of the laser emitted by the transmitting end is perpendicular to the main axis of the receiving field of view 2, F represents the transmitting control mirror, and the angle of the transmitting control mirror is adjusted to make the first transmitting field of view 1 shoot vertically upward, the first transmitting field of view 1 is on the left side of the receiving field of view 2 and intersects with the receiving field of view 2, the near end of the first transmitting field of view 1 does not touch the receiving field of view 2, the middle end partially touches the receiving field of view 2, and the far end is completely surrounded by the receiving field of view 2. Then, only the angle of the transmitting control mirror is changed, and the angle and position of the transmitting end are not changed, so that the second transmitting field of view 3 passes through the receiving field of view 2 from left to right.

[0023] like Figure 2 As shown, the first emission field of view 1 is composed of a direct blind area, a direct transition area and a direct full area from near to far; Figure 2 A represents the direct full area, and the data in the direct full area can be collected by the receiver. B represents the direct transition area, and part of the data in the direct transition area can be collected by the receiver. After processing the data in the direct transition area, the full-field signal data can also be obtained. C represents the direct blind area, and the data in the direct blind area cannot be collected by the receiver.

[0024] The second transmitting field of view 3 is composed of the first oblique blind area, the first oblique transition area, the oblique full area, the second oblique transition area and the second oblique blind area from near to far. The first oblique blind area is located on the left side of the receiving field of view 2, and the second oblique blind area is located on the right side of the receiving field of view 2. Figure 2 In the figure, a represents the first oblique blind zone, and the data in the first oblique blind zone cannot be collected by the receiving end. b represents the first oblique transition zone, and part of the data in the first oblique transition zone can be collected by the receiving end. c represents the oblique full zone, and the data in the oblique full zone can be collected by the receiving end. e represents the second oblique transition zone, and part of the data in the second oblique transition zone can be collected by the receiving end. f represents the second oblique blind zone, and the data in the second oblique blind zone cannot be collected by the receiving end. By processing the data in the first oblique transition zone and the second oblique transition zone, the full-field signal data can also be obtained. The blind area is the area where the transmitting field of view and the receiving field of view 2 do not intersect, the transition area is the area where the transmitting field of view and the receiving field of view 2 partially intersect, and the filled area is the area where the transmitting field of view is included in the receiving field of view 2.

[0025] The upper limit of the second oblique transition zone is higher than the lower limit of the vertical transition zone. Figure 2 As shown, when the inclined filling area does not overlap with the vertical transition area, the inclined filling area is below the vertical transition area, and the second inclined transition area partially overlaps with the vertical transition area and does not overlap with the vertical filling area.

[0026] By adjusting the tilt angle of the launch control mirror, technicians in this field may find other situations. For example, in the second situation, when the vertical filling area partially overlaps with the oblique filling area, the vertical transition area completely overlaps with the oblique filling area, and the second oblique transition area completely overlaps with the vertical filling area.

[0027] In the third case, when the vertical transition zone partially overlaps with the oblique filling zone, the second oblique transition zone overlaps with the vertical filling zone and the vertical transition zone respectively, or the vertical filling zone completely overlaps with the second oblique transition zone.

[0028] The data obtained by the receiving end of S3 includes high-altitude echo data and low-altitude echo data. The high-altitude echo data uses the data obtained in the direct transition zone and the direct full zone, and the low-altitude echo data uses the data obtained in the first oblique transition zone, the oblique full zone and the second oblique transition zone. The obtained high-altitude echo data and low-altitude echo data are spliced ​​to reduce the echo data in the blind spot, and the signal in the transition zone is converted into a full-field signal by referring to the paper "Analysis and Measurement of LiDAR Geometric Factors" (author Wang Shaolin).

[0029] like Figure 2 As shown, M represents the transmitting end, which includes a transmitting laser, N represents the receiving end, which includes a receiving optical system; the receiving optical system is connected to the receiving electrical system, P represents the receiving electrical system, the receiving electrical system is connected to the data processing system, and Q represents the data processing system. The receiving optical system includes a telescope, which generates a receiving field of view 2. The right side of the first oblique transition zone coincides with the receiving field of view 2, and the left side of the second oblique transition zone coincides with the receiving field of view 2. The right side of the vertical transition zone coincides with the receiving field of view 2. Example 2

[0030] Assume that the telescope aperture is D=200mm, the receiving field of view 2 generated is R=1mrad, the receiving half field of view is 0.5mrad, the transmitting laser beam generated by the transmitting laser is d=20mm, the transmitting field of view is r=0.1mrad, and the center distance between the telescope and the transmitting laser beam is 150mm.

[0031] like Figure 3As shown, when emitting a laser beam vertically, when emitting the first emission field of view 1 parallel to the main axis of the receiving field of view of the receiving field of view 2, it has an emission half field of view of 0.5 mrad. The height of the lower threshold of the vertical transition zone is h1=72.7m, and the height of the upper threshold of the vertical transition zone is h2=133.3m. Therefore, the first emission field of view 1 has a direct blind zone below 72.7m from near to far, a direct transition zone between 72.7m and 133.3m, and a direct full zone above 133.3m. In the absence of the emission control mirror device of this patent, the signal in the transition zone can be converted into a full field of view signal through geometric factor correction (refer to Wang Shaolin's paper), so the actual blind zone is 72.7m.

[0032] like Figure 4 As shown, when the angle of the emission control mirror is changed to emit the second emission field of view 3 with an angle to the main axis of the receiving field of view, the emission half field of view has a 0.5 mrad. The height of the lower threshold of the first oblique transition zone is h3=11.3m, the height of the upper threshold of the first oblique transition zone is h4=17.4, the height of the upper threshold of the oblique full zone is h5=94.1, and the height of the upper threshold of the second oblique transition zone is h4=106.1m. Therefore, the second emission field of view 3 from near to far produces the first oblique blind zone below 11.3m, the first oblique transition zone between 11.3m and 17.4m, the oblique full zone between 17.4m and 94.1m, the second oblique transition zone between 94.1m and 106.1m, and the second oblique blind zone above 106m.

[0033] After obtaining the two parts of data, the data of the direct transition zone, direct full zone, the first oblique transition zone, the oblique full zone, and the second oblique transition zone calculated above are spliced. The high-altitude echo data uses the data obtained from the direct transition zone and the direct full zone, and the low-altitude echo data uses the data obtained from the first oblique transition zone, the oblique full zone, and the second oblique transition zone. The high-altitude echo data and the low-altitude echo data are spliced ​​to reduce the echo data in the blind area, which can reduce the blind area from 72.7m to 11.3m.

[0034] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for reducing the blind area of ​​an atmospheric laser radar, characterized in that: include: S1. The transmitting end emits a laser beam through a transmitting control mirror to form a first transmitting field of view, so that the main axis of the first transmitting field of view is parallel to the main axis of the receiving field of view of the receiving end; S2. Change the angle of the launch control mirror, the launch end emits a laser beam through the launch control mirror to form a second launch field of view, the second launch field of view main axis and the receiving field of view main axis have an angle; S3. The receiving end transmits the acquired data to the data processing system for processing through photoelectric conversion.

2. The method for reducing the blind area of ​​atmospheric laser radar according to claim 1, characterized in that: The first transmitting field of view is in a paraxial relationship with the receiving field of view, and the receiving field of view partially overlaps with the first transmitting field of view; The second transmitting field of view extends through the receiving field of view.

3. The method for reducing the blind area of ​​atmospheric laser radar according to claim 1, characterized in that: The first emission field of view is, from near to far, a direct blind zone, a direct transition zone, and a direct full zone; the second emission field of view is, from near to far, a first oblique blind zone, a first oblique transition zone, an oblique full zone, a second oblique transition zone, and a second oblique blind zone.

4. The method for reducing the blind area of ​​atmospheric laser radar according to claim 3, characterized in that: The blind area is the area where the transmitting field of view and the receiving field of view do not intersect, the transition area is the area where the transmitting field of view and the receiving field of view partially intersect, and the filled area is the area where the transmitting field of view is included in the receiving field of view.

5. The method for reducing the blind area of ​​atmospheric laser radar according to claim 3, characterized in that: The emission control mirror adjusts the tilt angle so that the upper limit of the second oblique transition zone is higher than the lower limit of the vertical transition zone.

6. A method for reducing the blind area of ​​an atmospheric laser radar according to claim 5, characterized in that: The data obtained by the receiving end in S3 includes high-altitude echo data and low-altitude echo data. The high-altitude echo data uses the data obtained in the direct transition zone and the direct full zone, and the low-altitude echo data uses the data obtained in the first oblique transition zone, the oblique full zone and the second oblique transition zone; the obtained high-altitude echo data and low-altitude echo data are spliced ​​to reduce the echo data in the blind zone.

7. The method for reducing the blind area of ​​atmospheric laser radar according to claim 1, characterized in that: The transmitting end includes a transmitting laser, and the receiving end includes a receiving optical system; the receiving optical system is connected to the receiving electrical system, and the receiving electrical system is connected to the data processing system.

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