Underground engineering deformation anti-interference accurate monitoring system and method combining laser scanning and polarized light filtering

Abstract

The invention discloses an underground engineering deformation anti-interference accurate monitoring system and method combining laser scanning and polarized light filtering, the system comprises a three-dimensional laser scanner, a polarization control assembly and a control system, the polarization control assembly comprises a transmitting end linear polarizer, a receiving end circular polarization filter and a high-precision stepping motor; the three-dimensional laser scanner comprises a laser transmitting module and a laser receiving module, a transmitting end linear polarizer is mounted in front of the laser transmitting module, and a receiving end circular polarization filter is mounted in front of the laser receiving module; the high-precision stepping motor drives the receiving end circular polarization filter to rotate; the control system inputs the reflected laser intensity into a control circuit, analyzes the reflected laser intensity in real time and controls the high-precision stepping motor to adjust the rotation angle of the receiving end circular polarization filter. According to the invention, laser scanning and polarized light filtering technologies are combined, and interference signals of mirror reflection caused by glass or water leakage and the like are effectively filtered by dynamically adjusting the polarization angle.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering monitoring, and relates to a deformation monitoring system and method combining laser scanning and optical filtering. Background Art

[0002] Structural deformation is a common safety hazard during the construction and operation of underground projects (such as tunnels, mines, and underground pipeline corridors). Failure to monitor it promptly can lead to serious accidents such as collapse and leakage, threatening personnel safety and project stability. While traditional monitoring methods can provide sufficient data, they suffer from insufficient accuracy, low efficiency, and poor interference resistance.

[0003] While laser scanning technology currently provides high-precision 3D point cloud data, in complex underground environments, interference from reflected light (such as specular reflections from glass or leaking water) can significantly degrade data quality, making deformation difficult to identify. Furthermore, traditional filtering algorithms require post-processing and are unable to meet the needs of real-time monitoring.

[0004] Therefore, there is an urgent need for a deformation monitoring method that can automatically suppress environmental noise from the signal source and improve monitoring accuracy. Summary of the Invention

[0005] To address the inaccurate and real-time performance issues of existing laser scanning deformation monitoring technology, the present invention provides an interference-resistant, precise monitoring method for underground engineering deformation that combines laser scanning with polarized light filtering. This method combines laser scanning and polarized light filtering technologies to dynamically adjust the polarization angle to effectively filter out interference signals caused by specular reflections from glass or water seepage, thereby improving the accuracy and real-time performance of deformation identification and ensuring the safe operation of underground projects. This method can be used for real-time, high-precision deformation detection of structures such as tunnels, mines, and underground pipeline corridors.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A precise, anti-interference monitoring system for underground engineering deformation that combines laser scanning and polarization filtering includes a three-dimensional laser scanner, a polarization control component, and a control system, wherein:

[0008] The polarization control assembly includes a linear polarizer at the transmitting end, a circular polarization filter at the receiving end, and a high-precision stepping motor;

[0009] The three-dimensional laser scanner includes a laser emitting module and a laser receiving module, which are used to emit lasers and receive reflected signals to generate high-precision point cloud data;

[0010] The emitting end linear polarizer is installed in front of the laser emitting module to polarize the laser;

[0011] The receiving end circular polarization filter is installed in front of the laser receiving module to filter noise reflected light;

[0012] The high-precision stepping motor is used to drive the circular polarization filter at the receiving end to rotate;

[0013] The control system is equipped with a PID control algorithm. By inputting the reflected laser intensity received by the three-dimensional laser scanner into the control circuit, the reflected light intensity is analyzed in real time and a high-precision stepper motor is controlled to adjust the rotation angle of the circular polarization filter at the receiving end.

[0014] A method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarization filtering includes the following steps:

[0015] Step 1: Use a 3D laser scanner to emit laser light, and obtain horizontally polarized laser light after passing through a linear polarizer fixed in front of a laser emission module of the 3D laser scanner;

[0016] Step 2: Laser reflection causes changes in laser polarization characteristics:

[0017] The polarization changes of horizontally polarized laser light after encountering glass reflection are as follows: if the incident angle is close to the Brewster angle, the reflected light tends to be completely polarized, and the polarization direction is perpendicular to the incident plane. Eventually, the polarization degree and polarization direction may change to linearly polarized light. If the incident angle differs greatly from the Brewster angle, the reflected light tends to be partially polarized, and is partially polarized light.

[0018] The polarization changes of horizontally polarized laser light after it is reflected from the water surface are as follows: when the incident angle is close to Brewster, the reflected light is highly polarized, or the polarization direction of the reflected light is perpendicular to the incident plane. Eventually, the polarization degree may increase and the polarization direction may change, becoming partially polarized light.

[0019] The polarization of a horizontally polarized laser beam after reflection from a concrete surface changes as follows: The rough surface structure of the concrete causes multiple diffuse reflections, which disrupts the polarization direction. Most of the reflected light has a random polarization direction, and ultimately, the degree of polarization is significantly reduced, almost completely losing its polarization characteristics.

[0020] Step 3: A receiving-end circular polarization filter is set in front of the laser receiving module of the 3D laser scanner. By adjusting the rotation angle of the receiving-end circular polarization filter, the reflected laser signal with specific polarization characteristics is selectively transmitted at a specific angle, thereby distinguishing the structure signal reflected on the surface to be measured from the non-structure noise signal reflected on the non-measurement surface;

[0021] Step 4: Integrate a control system equipped with a PID control algorithm to input the intensity of the reflected laser light received by the 3D laser scanner into the control system, analyze the reflected light intensity in real time, and control a high-precision stepper motor to adjust the rotation angle of the circular polarization filter at the receiving end;

[0022] Step 5: Based on the filtered laser scanning data, use the inverse distance weighted method to interpolate the point cloud area, obtain a continuous three-dimensional laser cloud map, and calculate the deformation.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. Reduced reflected laser interference and improved anti-interference capabilities. Traditional laser scanning is easily affected by mirror reflections from glass, water seepage, and other surfaces, generating point cloud noise. This invention uses polarization filtering technology to distinguish surface material characteristics, effectively filtering out high-polarization noise signals from mirror reflections while retaining the real, low-polarization signals from diffuse reflections, significantly improving the data signal-to-noise ratio.

[0025] 2. Improve signal processing efficiency and enhance real-time monitoring. Traditional methods rely on post-processing filtering. This invention uses an algorithm to control hardware to achieve polarization filtering, directly suppressing noise during the data acquisition stage, eliminating post-processing time and solving the data processing lag problem of traditional monitoring methods.

[0026] 3. Combined with inverse distance weighted interpolation, it has the ability to monitor continuous deformation. Traditional discrete point clouds cannot intuitively reflect the overall deformation trend. This invention uses the inverse distance weighted method to interpolate the filtered high-precision point cloud to construct a continuous deformation surface, eliminate data gaps, and achieve full-area monitoring of the deformation field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the anti-interference and precise monitoring method for underground engineering deformation using a combination of laser scanning and polarization filtering. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0029] The present invention provides an anti-interference and precise monitoring system for underground engineering deformation combining laser scanning and polarized light filtering. Figure 1 As shown, the system consists of a three-dimensional laser scanner, a polarization control component and a control system, wherein:

[0030] The polarization control assembly includes a linear polarizer at the transmitting end, a circular polarization filter at the receiving end, and a high-precision stepping motor;

[0031] The three-dimensional laser scanner is used to emit laser light and receive reflected signals to generate high-precision point cloud data;

[0032] The three-dimensional laser scanner includes a laser emitting module and a laser receiving module, which are used to emit lasers and receive reflected signals to generate high-precision point cloud data;

[0033] The emitting end linear polarizer is installed in front of the laser emitting module to polarize the laser;

[0034] The receiving end circular polarization filter is installed in front of the laser receiving module and can be rotated and adjusted (controlled by a high-precision motor) to filter noise reflected light;

[0035] The high-precision stepper motor adopts a closed-loop control servo motor to drive the circular polarization filter at the receiving end to rotate, with an angle adjustment accuracy of ±0.1°;

[0036] The control system is equipped with a PID control algorithm, which inputs the intensity of the reflected laser received by the 3D laser scanner into the control circuit, analyzes the intensity of the reflected light in real time, and controls the high-precision stepper motor to adjust the rotation angle of the circular polarization filter at the receiving end;

[0037] The three-dimensional laser scanner is fixedly connected to the linear polarizer at the transmitting end to ensure that the emitted laser has a single polarization direction; the circular polarization filter at the receiving end is connected to the high-precision stepper motor through a coupling, and the high-precision stepper motor is driven by the control system; the control system receives the reflected light intensity signal of the three-dimensional laser scanner and dynamically adjusts the rotation angle of the high-precision stepper motor.

[0038] The present invention also provides a method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarized light filtering. Figure 1 As shown, the method obtains laser scanning data and calculates deformation by comparing the light intensity of the emitted laser and the received laser, and specifically includes the following steps:

[0039] Step 1: Use the 3D laser scanner laser emission module to emit laser light. The angle between the polarization plane of the linear polarizer at the emission end and the horizontal plane is fixed at 0° to obtain horizontally polarized laser light. This ensures that the polarization direction of all emitted laser light is consistent, reducing the complexity of subsequent filtering.

[0040] Step 2: Laser reflection causes changes in laser polarization characteristics:

[0041] The polarization changes of horizontally polarized laser light after encountering glass reflection are as follows: if the incident angle is close to the Brewster angle, the reflected light tends to be completely polarized, and the polarization direction is perpendicular to the incident plane. Eventually, the polarization degree and polarization direction may change to linearly polarized light. If the incident angle differs greatly from the Brewster angle, the reflected light tends to be partially polarized, and is partially polarized light.

[0042] The polarization changes of horizontally polarized laser light after it is reflected from the water surface are as follows: when the incident angle is close to Brewster, the reflected light is highly polarized, or the polarization direction of the reflected light is perpendicular to the incident plane. Eventually, the polarization degree may increase and the polarization direction may change, becoming partially polarized light.

[0043] The polarization changes of horizontally polarized laser light after being reflected from the concrete surface are as follows: Due to the rough structure of the concrete surface, multiple diffuse reflections cause the polarization direction to be broken up, and the polarization direction of most reflected light becomes random. Ultimately, the polarization degree is greatly reduced, and the polarization characteristics are almost lost.

[0044] Step 3: A receiving-end circular polarization filter is set in front of the laser receiving module of the 3D laser scanner to selectively transmit reflected laser signals with specific polarization characteristics. By adjusting the rotation angle of the receiving-end circular polarization filter, the transmittance of the target structure surface reflected signal relative to noise signals such as mirror reflection is increased, effectively suppressing polarization distortion or polarization-enhanced non-structural signals caused by factors such as mirror reflection and water surface interference. This process is based on the difference in the polarization characteristics of the reflected light to achieve optical differentiation between the effective signal of the target structure and the background noise, thereby improving the recognition accuracy of the deformed area. Specifically, after the polarized laser is reflected by a rough surface such as concrete, its polarization state is severely dispersed, and the reflected light is in an unpolarized or partially polarized state. When this type of light passes through the receiving-end circular polarization filter, regardless of the angle of the receiving-end circular polarization filter, it will be significantly attenuated, and the final received signal strength will drop by about 50% compared to the transmitted laser. However, when the laser is reflected by a relatively smooth surface such as glass or a leaking area, it still retains a strong polarization characteristic. By adjusting the rotation angle of the circular polarization filter at the receiving end, the reflected light can be completely filtered or transmitted to the maximum at a specific angle, achieving selective enhancement or suppression, thereby distinguishing between the structural signals reflected on the surface to be measured and the unstructured noise signals reflected on the non-measured surface.

[0045] Step 4: Combined with a control system equipped with a PID control algorithm, the reflected laser intensity received by the 3D laser scanner is input into the control system to analyze the reflected light intensity in real time and control the high-precision stepper motor to adjust the rotation angle of the circular polarization filter at the receiving end. The specific steps are as follows:

[0046] (1) Assume that the original horizontally polarized laser intensity is , after reflection, the receiving end signal may have the following possibilities:

[0047] Valid signal : Reflection from rough surfaces such as concrete, non-polarized light, ;

[0048] Interference noise : Reflection from glass or leaky area, partially polarized light, percentage , .

[0049] (2) Calculate the signal-to-noise ratio :

[0050]

[0051] (3) Determine the signal-to-noise ratio :

[0052] like >Threshold, maintain the current receiving end circular polarization filter angle;

[0053] like < threshold, start the PID control algorithm and adjust the angle of the circular polarization filter at the receiving end.

[0054] (4) If <Threshold:

[0055] High-precision stepper motor controls the rotation of the circular polarization filter at the receiving end Angle, calculate the signal-to-noise ratio again and record it as ;

[0056] like > ,renew And return to (3) to judge the signal-to-noise ratio ;

[0057] like < , the receiving end circular polarization filter rotates in the opposite direction Angle and return (3) to determine the signal-to-noise ratio .

[0058] (5) If >Threshold:

[0059] Save the current laser signal and complete the 3D laser scanning.

[0060] Step 5: Based on the filtered laser scanning data, use the inverse distance weighted method to interpolate the point cloud area, obtain a continuous 3D laser cloud map, and calculate the deformation. The specific steps are as follows:

[0061] (1) Scanning point cloud data matching:

[0062] Align the feature points of the current frame scan point cloud with the feature points of the previous frame scan point cloud to eliminate device displacement errors. The feature points are manually selected points on the surface of the structure that are considered to be non-displacement points.

[0063] (2) Spatial interpolation calculation:

[0064] The inverse distance weighted method is used to complete the area between the monitoring points and generate a continuous 3D laser cloud map of the current frame. The formula is as follows:

[0065]

[0066] Where, is the detection value of the point to be interpolated; is the measurement value of the i-th known monitoring point at time t; is the distance between the point to be interpolated and the i-th known monitoring point; is the distance weight index, which is generally 2; n is the number of known measurement points involved in the interpolation.

[0067] (3) Deformation quantification calculation:

[0068] The deformation is calculated using the following formula:

[0069]

[0070] Where, is the deformation of point i; Calculate the horizontal coordinate of the point at time t; Calculate the vertical coordinate of the point at time t; Calculate the vertical coordinate of the point at time t.

Claims

1. A combined laser scanning and polarization filtering underground engineering deformation anti-interference precision monitoring system, characterized by The deformation monitoring system includes a three-dimensional laser scanner, a polarization control component and a control system, wherein: The polarization control assembly includes a linear polarizer at the transmitting end, a circular polarization filter at the receiving end, and a high-precision stepping motor; The three-dimensional laser scanner includes a laser emitting module and a laser receiving module, which are used to emit lasers and receive reflected signals to generate high-precision point cloud data; The emitting end linear polarizer is installed in front of the laser emitting module to polarize the laser; The receiving end circular polarization filter is installed in front of the laser receiving module to filter noise reflected light; The high-precision stepping motor is used to drive the circular polarization filter at the receiving end to rotate; The control system is equipped with a PID control algorithm. By inputting the reflected laser intensity received by the three-dimensional laser scanner into the control circuit, the reflected light intensity is analyzed in real time and a high-precision stepper motor is controlled to adjust the rotation angle of the circular polarization filter at the receiving end.

2. The underground engineering deformation anti-interference precision monitoring system combining laser scanning and polarization filtering according to claim 1 is characterized in that The three-dimensional laser scanner is fixedly connected to the linear polarizer at the transmitting end to ensure that the emitted laser has a single polarization direction; the circular polarization filter at the receiving end is connected to the high-precision stepper motor through a coupling, and the high-precision stepper motor is driven by the control system; the control system receives the reflected light intensity signal of the three-dimensional laser scanner and dynamically adjusts the rotation angle of the high-precision stepper motor.

3. The underground engineering deformation anti-interference precision monitoring system combining laser scanning and polarization filtering according to claim 1 or 2 is characterized in that The angle adjustment accuracy of the high-precision stepper motor is ±0.1°.

4. A method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarized light filtering, characterized in that The method comprises the following steps: Step 1: Use a 3D laser scanner to emit laser light, and obtain horizontally polarized laser light after passing through a linear polarizer fixed in front of a laser emission module of the 3D laser scanner; Step 2: A receiving-end circular polarization filter is set in front of the laser receiving module of the 3D laser scanner. By adjusting the rotation angle of the receiving-end circular polarization filter, the reflected laser signal with specific polarization characteristics is selectively transmitted at a specific angle, thereby distinguishing the structure signal reflected on the surface to be measured from the non-structure noise signal reflected on the non-measurement surface; Step 3: Integrate a control system equipped with a PID control algorithm to input the intensity of the reflected laser light received by the 3D laser scanner into the control system, analyze the reflected light intensity in real time, and control a high-precision stepper motor to adjust the rotation angle of the circular polarization filter at the receiving end; Step 4: Based on the filtered laser scanning data, use the inverse distance weighted method to interpolate the point cloud area, obtain a continuous three-dimensional laser cloud map, and calculate the deformation.

5. The method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarization filtering according to claim 4 is characterized in that In the step 1, the angle between the polarization plane of the linear polarizer at the emitting end and the horizontal plane is fixed at 0°.

6. The method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarization filtering according to claim 4 is characterized in that The specific steps of step three are as follows: (1) Assume that the original horizontally polarized laser intensity is , after reflection, the receiving end signal may have the following possibilities: Valid signal : Reflection from rough surfaces such as concrete, non-polarized light, ; Interference noise : Reflection from glass or leaky area, partially polarized light, percentage ; (2) Calculate the signal-to-noise ratio : (3) Determine the signal-to-noise ratio : like >Threshold, maintain the current receiving end circular polarization filter angle; like < threshold, start the PID control algorithm and adjust the angle of the circular polarization filter at the receiving end; (4) If <Threshold: High-precision stepper motor controls the rotation of the circular polarization filter at the receiving end Angle, calculate the signal-to-noise ratio again and record it as ; like > ,renew And return to (3) to judge the signal-to-noise ratio ; like < , the circular polarization filter at the receiving end rotates in the opposite direction Angle and return (3) to determine the signal-to-noise ratio ; (5) If >Threshold: Save the current laser signal and complete the 3D laser scanning.

7. The method for accurately monitoring underground engineering deformation with anti-interference by combining laser scanning and polarization filtering according to claim 4 is characterized in that The specific steps of step 4 are as follows: (1) Scanning point cloud data matching: Align the feature points of the current frame scan point cloud with the feature points of the previous frame scan point cloud to eliminate device displacement errors; (2) Spatial interpolation calculation: The inverse distance weighted method is used to complete the area between the monitoring points and generate a continuous 3D laser cloud map of the current frame. The formula is as follows: Where, is the detection value of the point to be interpolated; is the measurement value of the i-th known monitoring point at time t; is the distance between the point to be interpolated and the i-th known monitoring point; is the distance weight index; n is the number of known measurement points involved in interpolation; (3) Deformation quantification calculation: Where, is the deformation of point i; Calculate the horizontal coordinate of the point at time t; Calculate the vertical coordinate of the point at time t; Calculate the vertical coordinate of the point at time t.

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