Visibility lidar for sea fog, fog bank monitoring

Abstract

The utility model relates to a laser radar technical field especially relates to a kind of visibility laser radar for sea fog, fog monitoring, including: laser emission module, optical receiving module, light splitting module, rudder module, detector and controller, optical receiving module receives backscattering signal, and this backscattering signal is transmitted to light splitting module, light splitting module processes this backscattering signal, to filter out non-signal light, signal light reaches detector by rudder module, detector converts optical signal into electrical signal, to obtain photon number, controller according to the photon number to control rudder module switching different channel.The utility model is by the way of dynamic regulation light path attenuation, to realize the full dynamic range detection of near field to far field, significantly improve the monitoring precision and reliability under the fast-changing meteorological conditions of sea fog, fog etc.

Description

Technical Field

[0001] This utility model relates to the field of lidar technology, and in particular to a visibility lidar for monitoring sea fog and dense fog. Background Technology

[0002] Visibility is a critical parameter in meteorology, transportation, navigation, and aviation, especially under low-visibility conditions such as sea fog and dense fog, where real-time and accurate monitoring is crucial for safety. Traditional visibility monitoring methods (e.g., transmission-type and scattering-type visibility meters) have drawbacks such as limited measurement range, susceptibility to environmental interference, and inability to provide spatial resolution information. LiDAR, with its high spatiotemporal resolution, active detection capabilities, and long-range measurement advantages, has become an ideal tool for visibility monitoring. However, existing LiDAR still faces two major challenges in high-concentration aerosol environments such as sea fog and dense fog: 1. Insufficient dynamic range: Strong near-field scattered signals can easily cause detector saturation, while weak far-field signals result in a low signal-to-noise ratio, which is difficult to balance in traditional fixed-gain systems. 2. Signal saturation leads to loss of detail: The rapid changes in fog require the system to have high dynamic response capability, but existing solutions (such as automatic gain control ADC or software compensation) have problems with delay or accuracy loss.

[0003] Currently, typical implementations of visibility lidar based on automatic gain control (AGC) or dual-channel detection include: 1. Dual detector scheme (e.g., dual-channel lidar receiving system): The received echo signal light is split into two beams by a beam splitter, and then focused onto two detectors by lenses. Different magnifications are set to achieve fine detection with a large dynamic range, which improves the detection capability and accuracy of lasers. However, it has problems such as high system complexity, high cost and difficulty in optical path calibration. 2. Electronic gain adjustment scheme: This scheme adapts to changes in signal strength by adjusting the detector bias voltage or amplifier gain, but it is limited by slow response speed and limited dynamic range, making it difficult to cope with the rapid fluctuations of fog. 3. Fixed attenuator switching scheme: Manual or motor-driven attenuators are set in the optical path, but the lack of real-time closed-loop feedback control makes it impossible to adapt to the signal saturation level, resulting in inaccurate switching timing or response delay. Utility Model Content

[0004] The technical problem to be solved by this utility model is: in order to solve the technical problems of insufficient dynamic range, control delay and hardware redundancy of existing visibility lidar, this utility model provides a visibility lidar for monitoring sea fog and fog patches. By improving the structure of the visibility lidar, it can cover the full range of linear signal detection from near field to far field, eliminate control delay and reduce hardware burden.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a visibility lidar for monitoring sea fog and fog patches, comprising: a laser emitting module, an optical receiving module, a beam splitting module, a servo module, a detector, a data processing and analysis module, and a controller. The laser emitting module is used to emit a laser beam. After the laser beam enters the atmosphere, it interacts with aerosols to generate a backscattered signal. The optical receiving module receives the backscattered signal and transmits it to the beam splitting module. The beam splitting module processes the backscattered signal to filter out non-signal light. The signal light passes through the servo module to reach the detector. The detector converts the optical signal into an electrical signal to obtain the photon count. The controller controls the servo module to switch different channels according to the photon count.

[0006] Therefore, by dynamically adjusting the attenuation of the optical path through the beam splitting module and the servo module, this lidar has a simpler structure and is easier to operate compared to existing visibility lidars. By dynamically adjusting the optical path attenuation, it can achieve full dynamic range detection from near field to far field. At the same time, it switches the servo module channel in real time according to the photon count, directly linking the signal saturation with the servo action to ensure short response time, adapt to the transient changes of fog, and eliminate control delay. The design of adjustable channel servo module and single detector replaces the multi-channel redundant design to improve system reliability, thereby reducing hardware burden and significantly improving the monitoring accuracy and reliability under rapidly changing weather conditions such as sea fog and fog patches. It is suitable for high-precision visibility monitoring needs in key fields such as traffic safety and maritime early warning.

[0007] As a further improvement to the above technical solution: the laser emitting module, the servo module, and the detector are all connected to the controller; the optical receiving module, the beam splitting module, and the detector are arranged sequentially along the receiving direction of the optical path; and the servo module is embedded in the beam splitting module.

[0008] As a further improvement to the above technical solution: the laser emitting module includes a laser, a beam shaper, a reflector, and a right-angle prism. The laser is connected to the controller. The laser, the beam shaper, the reflector, and the right-angle prism are arranged sequentially along the emission direction of the optical path. The laser is used to emit a laser beam. The beam shaper is used to shape the laser beam emitted by the laser. The reflector and the right-angle prism are both used to control the emission direction of the laser beam.

[0009] As a further improvement to the above technical solution: the optical receiving module includes a receiver and an aperture stop. The receiver, the aperture stop, the beam splitter, and the detector are arranged sequentially along the receiving direction of the optical path. The receiver is used to receive backscattered signals, and the aperture stop is used to allow signal light with an aperture size less than or equal to A to pass through while blocking stray light with an aperture size greater than A.

[0010] As a further improvement to the above technical solution: the beam splitting module includes a collimating lens, a filter, and a focusing lens. The optical receiving module, the collimating lens, the filter, the focusing lens, and the detector are arranged sequentially along the receiving direction of the optical path. The servo module is located between the filter and the focusing lens. The collimating lens is used to collimate the backscattered signal. The filter is used to filter the backscattered signal after collimation to filter out non-signal light. The servo module is used to attenuate the light intensity of the signal light. The attenuated signal light is focused onto the detector by the focusing lens so that the detector can operate normally and be in a non-saturated state.

[0011] As a further improvement to the above technical solution: the servo module includes: a first drive unit, a first gear position and a second gear position, the first gear position and the second gear position are both connected to the drive end of the first drive unit, the first gear position and the second gear position are located between the filter and the focusing lens, and the first drive unit is connected to the controller.

[0012] As a further improvement to the above technical solution: the signal at the first gear position is greater than the signal at the second gear position, the first gear position is equipped with an attenuator with a low attenuation ratio, and the second gear position is equipped with an attenuator with a high attenuation ratio.

[0013] As a further improvement to the above technical solution, the servo module further includes a second drive unit and a third gear position. The third gear position is mounted on the second drive unit, which is connected to the controller. When the third gear position is in a vertical state, it is located between the filter and the focusing lens. Thus, through the cooperation of the first and second drive units, combined operation of the first, second, and third gear positions is achieved. Furthermore, the third gear position prevents signal oversaturation and insufficient attenuation even in extremely low visibility environments, thus avoiding signal information loss due to signal saturation.

[0014] As a further improvement to the above technical solution: the third gear is equipped with an attenuation plate with an ultra-high attenuation ratio.

[0015] As a further improvement to the above technical solution: the multiplier of the first attenuator is less than that of the second attenuator, which is less than that of the third attenuator.

[0016] Compared with the prior art, the beneficial effects of this utility model are: 1. This utility model dynamically adjusts the attenuation of the optical path through a beam splitting module and a servo module. Compared with existing visibility lidar, this lidar has a simpler structure and is easier to operate. By dynamically adjusting the optical path attenuation, it achieves full dynamic range detection from near field to far field. At the same time, it switches the servo module channel in real time according to the photon count, directly linking the signal saturation with the servo action to ensure short response time and adapt to the transient changes of fog, thus eliminating control delay. The design of an adjustable channel servo module and a single detector replaces the multi-channel redundant design to improve system reliability, thereby reducing hardware burden and significantly improving the monitoring accuracy and reliability under rapidly changing weather conditions such as sea fog and fog patches. It is suitable for high-precision visibility monitoring needs in key fields such as traffic safety and maritime early warning.

[0017] 2. This utility model achieves combined operation of the first gear, the second gear, and the third gear through the cooperation of the first driving component and the second driving component. In addition, the third gear prevents the signal from being oversaturated due to insufficient attenuation in extremely low visibility environments, thus avoiding the loss of signal information due to signal saturation. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Figure 1 This is a system block diagram of the visibility lidar for monitoring sea fog and dense fog according to this utility model; Figure 2 This is a schematic diagram of the visibility lidar for monitoring sea fog and dense fog according to the present invention. Figure 3 This is a schematic diagram of the servo module of this utility model; Figure 4 This is a control block diagram of the visibility lidar for monitoring sea fog and dense fog according to this utility model.

[0020] In the diagram: 1. Laser emitting module; 101. Laser; 102. Beam shaper; 103. Mirror; 104. Right-angle prism; 2. Optical receiving module; 201. Receiver; 202. Aperture; 3. Spectrometer module; 301. Collimating lens; 302. Filter; 303. Focusing lens; 4. Servo module; 401. First drive component; 402. First gear position; 403. Second gear position; 404. Second drive component; 405. Third gear position; 5. Detector; 6. Controller. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0022] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0024] like Figures 1 to 4 The diagram shows the preferred embodiment of this utility model. The visibility lidar for monitoring sea fog and dense fog in this embodiment includes: a laser emitting module 1, an optical receiving module 2, a beam splitting module 3, a servo module 4, a detector 5, and a controller 6. The laser emitting module 1 emits a laser beam. After the laser beam enters the atmosphere, it interacts with aerosols to generate a backscattering signal. The optical receiving module 2 receives the backscattering signal and transmits it to the beam splitting module 3. The beam splitting module 3 processes the backscattering signal to filter out non-signal light. The signal light passes through the servo module 4 to reach the detector 5. The detector 5 converts the optical signal into an electrical signal to obtain the photon count. The controller 6 controls the servo module 4 to switch different channels based on the photon count. Therefore, by dynamically adjusting the attenuation of the optical path through the beam splitter module 3 and the servo module 4 (i.e., the attenuator of the servo module 4 switches at millisecond levels), compared with existing visibility lidar, this lidar has a simpler structure and is easier to operate. By dynamically adjusting the attenuation of the optical path, it can achieve full dynamic range detection from near field (i.e., high attenuation) to far field (i.e., low attenuation). At the same time, the channel of the servo module 4 is switched in real time according to the photon count, directly linking the signal saturation with the servo action, ensuring a short response time, adapting to the transient changes of fog, and eliminating control delay. The design of adjustable channel servo module 4 and single detector 5 replaces the multi-channel redundant design, thereby improving the reliability of the system and reducing the hardware burden (i.e., not only reducing the failure rate, but also ensuring long-term stability of attenuation accuracy through closed-loop feedback). It significantly improves the monitoring accuracy and reliability under rapidly changing weather conditions such as sea fog and fog patches, and is suitable for high-precision visibility monitoring needs in key areas such as traffic safety and maritime early warning.

[0025] In other words, by controlling the number of photons to switch different channels using the servo module 4, the collaborative design of the beam splitter module 3 and the attenuator, and the closed-loop control of the servo module 4 (i.e., adaptive switching of attenuators with different attenuation ratios) can be achieved. This enables the visibility lidar used for monitoring sea fog and dense fog to adaptively adjust to different weather conditions (i.e., reduce the light intensity in real time before the signal reaches the saturation threshold; through a segmented attenuation strategy, the application of the lidar's large dynamic range is expanded, covering all scenarios from dense fog to clear skies, and meeting the needs of refined detection). This improves the adaptability and measurement effect of the visibility lidar used for monitoring sea fog and dense fog in various weather environments, especially for application scenarios involving low visibility sea fog and dense fog.

[0026] In other words, it can achieve various weather conditions from clear skies to low visibility; based on the different signal strength characteristics corresponding to different weather conditions, the closed-loop control servo module 4 is used; and the attenuator with different ratios is switched according to the signal saturation level, so as to achieve the goal of balancing signal and signal-to-noise ratio under different weather conditions. It can effectively solve the problem of traditional lidar where the signal increases rapidly when the external visibility environment drops to a relatively low level, resulting in detector saturation and insufficient dynamic range, while ensuring good signal quality in clear skies. Through gain adjustment under different signal strength environments, it can also ensure the monitoring of subtle fog structure information in low visibility environments.

[0027] In other words, due to the drastic changes in aerosol concentration in scenarios such as sea fog and dense fog, strong near-field scattering signals (leading to detector 5 saturation) coexist with weak far-field signals (signal-to-noise ratio degradation). Existing methods mostly rely on fixed-gain detection (a compatibility balance achieved by the lidar during factory settings to accommodate various conditions from clear skies with high visibility to foggy skies with low visibility; however, in extreme situations (e.g., in sea fog with low visibility, insufficient attenuation due to strong signal can lead to signal saturation and poor measurement results)) or open-loop adjustment mechanisms (e.g., dual-channel detector 5 or electronic gain control). This design approach leads to the following problems: insufficient dynamic range (i.e., near-field signal...). The present application addresses several issues: signal saturation or low far-field signal-to-noise ratio leading to data distortion, control delay (i.e., inability to track rapid changes in fog, resulting in loss of temporal resolution), and hardware redundancy (i.e., the dual-detector 5 method increases system complexity and cost). This application achieves full dynamic range detection from near-field (high attenuation) to far-field (low attenuation) by dynamically adjusting optical path attenuation. It switches the servo module 4 channels in real-time based on photon count, directly linking signal saturation to servo action, ensuring short response time, adapting to fog transients, and eliminating control delay. The design of an adjustable-channel servo module 4 and a single detector 5 replaces the multi-channel redundant design, improving system reliability and reducing hardware burden.

[0028] Specifically, detector 5 is a single-photon detector 5, which converts optical signals into electrical signals (i.e., photoelectric conversion of echo signals), and has the characteristics of strong detection performance, low dark current, and high sensitivity; the wavelength of laser 101 is 1064nm, therefore, APD detector 5 is used to detect the 1064nm signal. If ultraviolet-visible laser 101 (e.g., wavelength of 532nm) is used, PMT detector 5 is selected for detection.

[0029] In this embodiment, the laser emitting module 1, the servo module 4, and the detector 5 are all connected to the controller 6. The optical receiving module 2, the beam splitting module 3, and the detector 5 are arranged sequentially along the receiving direction of the optical path, and the servo module 4 is embedded in the beam splitting module 3.

[0030] In this embodiment, the laser emitting module 1 includes a laser 101, a beam shaper 102, a reflector 103, and a right-angle prism 104. The laser 101 is connected to the controller 6. The laser 101, beam shaper 102, reflector 103, and right-angle prism 104 are arranged sequentially along the emission direction of the optical path. The laser 101 is used to emit a laser beam. The beam shaper 102 is used to shape the laser beam emitted by the laser 101. The reflector 103 and right-angle prism 104 are both used to control the emission direction of the laser beam from the laser 101.

[0031] Specifically, laser 101 can also be replaced by other devices that can emit laser beams. The wavelength of the laser beam emitted by laser 101 can be 532nm, 1030nm, or 1064nm. Beam shaper 102 refers to a device or module that has the functions of intensity distribution shaping, divergence angle control, and wavefront adjustment.

[0032] In this embodiment, the optical receiving module 2 includes a receiver 201 and an aperture 202. The receiver 201, aperture 202, beam splitter 3, and detector 5 are arranged sequentially along the receiving direction of the optical path. The receiver 201 is used to receive backscattered signals, and the aperture 202 is used to allow signal light with an aperture A less than or equal to the aperture size to pass through while blocking stray light with an aperture larger than the aperture size.

[0033] For example, receiver 201 typically uses a transmission telescope or a Cassegrain telescope.

[0034] In this embodiment, the beam splitting module 3 includes a collimating lens 301, a filter 302, and a focusing lens 303. The optical receiving module 2, collimating lens 301, filter 302, focusing lens 303, and detector 5 are arranged sequentially along the receiving direction of the optical path. The servo module 4 is located between the filter 302 and the focusing lens 303. The collimating lens 301 is used to collimate the backscattered signal. The filter 302 is used to filter the backscattered signal after collimation to filter out non-signal light. The servo module 4 is used to attenuate the light intensity of the signal light. The attenuated signal light is focused onto the detector 5 through the focusing lens 303 so that the detector 5 can operate normally and be in a non-saturated state.

[0035] Specifically, the collimating lens 301 is used to collimate the backscattered signal to ensure that the out-of-band light suppression capability of the filter 302 is maximized.

[0036] In this embodiment, the servo module 4 includes: a first drive unit 401, a first gear position 402, a second gear position 403, a second drive unit 404, and a third gear position 405. The first gear position 402 and the second gear position 403 are both connected to the drive end of the first drive unit 401. The first gear position 402 and the second gear position 403 are located between the filter 302 and the focusing lens 303. The first drive unit 401 is connected to the controller 6. The third gear position 405 is mounted on the second drive unit 404. The second drive unit 404 is connected to the controller. The system is connected in six phases. When the third position 405 is in a vertical state, it is located between the filter 302 and the focusing lens 303. The signal of the first position 402 is greater than that of the second position 403. The first position 402 is equipped with a low attenuation ratio attenuator, the second position 403 is equipped with a high attenuation ratio attenuator, and the third position 405 is equipped with an ultra-high attenuation ratio attenuator. The attenuator ratio of the first position 402 is less than that of the second position 403, which is less than that of the third position 405. Thus, through the cooperation of the first driving component 401 and the second driving component 404, the combined operation of the first position 402, the second position 403, and the third position 405 is achieved. In addition, the third position 405 prevents insufficient attenuation and signal oversaturation in extremely low visibility environments, thus avoiding signal information loss due to signal saturation.

[0037] For example, the first driving component 401 is a motor, and the second driving component 404 is a motor.

[0038] The working principle of this invention is as follows: First, a laser beam is emitted by laser 101 and shaped by beam shaper 102. Then, the emission direction of the shaped laser beam is adjusted by reflector 103 and right-angle prism 104. Next, receiver 201 receives the backscattered signal (i.e., echo signal). Then, the backscattered signal passes through beam splitting module 3 and servo module 4 to reach detector 5. Detector 5 converts the optical signal into an electrical signal to obtain the photon count. Finally, if the photon count is greater than or equal to a threshold (this threshold is empirical), the photon count is determined. If the threshold is set to 180,000 photons, the first driving unit 401 is activated to switch the first position 402 to the second position 403 (i.e., switching is performed by controlling the rotation of the first position 402 and the second position 403 through the first driving unit 401). The photon count is then judged again. If the photon count is still greater than or equal to the threshold, the second driving unit 404 is activated to rotate the third position 405 between the filter 302 and the focusing lens 303. Otherwise, the first driving unit 401 is not activated to avoid loss of signal information due to signal saturation.

[0039] In summary, this invention dynamically adjusts the attenuation of the optical path through the beam splitting module 3 and the servo module 4. Compared with existing visibility lidar, this lidar has a simpler structure and is easier to operate. By dynamically adjusting the optical path attenuation, it achieves full dynamic range detection from near field to far field. At the same time, it switches the channel of the servo module 4 in real time according to the photon count, directly linking the signal saturation with the servo motor's action, ensuring a short response time and adapting to the transient changes of fog, thus eliminating control delay. The design of an adjustable channel servo module 4 and a single detector 5 replaces the multi-channel redundant design, improving system reliability and reducing hardware burden. It significantly improves the monitoring accuracy and reliability under rapidly changing weather conditions such as sea fog and fog patches, and is suitable for high-precision visibility monitoring needs in key areas such as traffic safety and maritime early warning.

[0040] The above description is based on the preferred embodiments of this utility model. Through the above explanation, those skilled in the art can make various changes and modifications without departing from the technical concept of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A visibility lidar for monitoring sea fog and patch fog, characterized in that, include: Laser emitting module (1), the laser emitting module (1) is used to emit a laser beam, which interacts with aerosols after entering the atmosphere to generate a backscattering signal; The optical receiving module (2), the beam splitting module (3), the servo module (4), the detector (5), and the controller (6) are configured. The optical receiving module (2) receives the backscattered signal and transmits it to the beam splitting module (3). The beam splitting module (3) processes the backscattered signal to filter out non-signal light. The signal light passes through the servo module (4) and reaches the detector (5). The detector (5) converts the optical signal into an electrical signal to obtain the number of photons. The controller (6) controls the servo module (4) to switch different channels according to the number of photons.

2. The visibility lidar for monitoring sea fog and patch fog according to claim 1, characterized in that, The laser emitting module (1), the servo module (4) and the detector (5) are all connected to the controller (6). The optical receiving module (2), the beam splitting module (3) and the detector (5) are arranged sequentially along the receiving direction of the optical path. The servo module (4) is embedded in the beam splitting module (3).

3. The visibility lidar for monitoring sea fog and patch fog according to claim 1, characterized in that, The laser emitting module (1) includes: The laser (101), beam shaper (102), reflector (103), and right-angle prism (104) are connected to the controller (6). The laser (101), beam shaper (102), reflector (103), and right-angle prism (104) are arranged sequentially along the emission direction of the optical path. The laser (101) is used to emit a laser beam. The beam shaper (102) is used to shape the laser beam emitted by the laser (101). The reflector (103) and right-angle prism (104) are both used to control the emission direction of the laser beam of the laser (101).

4. The visibility lidar for monitoring sea fog and patch fog according to claim 1, characterized in that, The optical receiving module (2) includes: The receiver (201) and the aperture (202) are arranged in sequence along the receiving direction of the optical path. The receiver (201) is used to receive backscattered signals, and the aperture (202) is used to allow signal light with an aperture A less than or equal to the aperture and to block stray light with an aperture greater than the aperture.

5. The visibility lidar for monitoring sea fog and patch fog according to claim 1, characterized in that, The beam splitting module (3) includes: The collimating lens (301), filter (302), and focusing lens (303) are arranged sequentially along the receiving direction of the optical path. The servo module (4) is located between the filter (302) and the focusing lens (303). The collimating lens (301) is used to collimate the backscattered signal. The filter (302) is used to filter the backscattered signal after collimation to filter out non-signal light. The servo module (4) is used to attenuate the light intensity of the signal light. The attenuated signal light is focused onto the detector (5) by the focusing lens (303) so that the detector (5) can operate normally and be in a non-saturated state.

6. The visibility lidar for monitoring sea fog and patch fog according to claim 5, characterized in that, The servo module (4) includes: The first drive unit (401), the first gear position (402), and the second gear position (403) are connected to the drive end of the first drive unit (401). The first gear position (402) and the second gear position (403) are located between the filter (302) and the focusing lens (303). The first drive unit (401) is connected to the controller (6).

7. The visibility lidar for monitoring sea fog and patch fog according to claim 6, characterized in that, The signal of the first gear (402) is greater than the signal of the second gear (403). The first gear (402) is equipped with an attenuator with a low attenuation ratio, and the second gear (403) is equipped with an attenuator with a high attenuation ratio.

8. The visibility lidar for monitoring sea fog and patch fog according to claim 7, characterized in that, The servo module (4) also includes: A second drive unit (404) and a third gear position (405), wherein the third gear position (405) is mounted on the second drive unit (404), and the second drive unit (404) is connected to the controller (6); When the third position (405) is in a vertical state, the third position (405) is located between the filter (302) and the focusing lens (303).

9. The visibility lidar for monitoring sea fog and patch fog according to claim 8, characterized in that, The third gear (405) is equipped with an attenuator with an ultra-high attenuation ratio.

10. The visibility lidar for monitoring sea fog and patch fog according to claim 9, characterized in that, The attenuation factor of the first gear (402) is less than that of the second gear (403) attenuation factor, which is less than that of the third gear (405) attenuation factor.

Images