UAV-Borne LiDAR Scanning Mirror and Shielding for Water Depth Accuracy
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Solution Overview
Problem
Existing LiDAR laser scanning devices are not suitable for water-bottom measurement environments due to low diffuse reflectance from water bottoms, high light absorption, and scattering, leading to inaccurate measurements.
Innovation Solution
A laser scanning device for UAV-borne LiDAR with a light-plane reflecting rotating mirror, notched annular shield, and photodetector protection assembly, utilizing synchronous optical scanning and light attenuation/occlusion to enhance measurement accuracy and reduce complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional laser scanning devices are used for water depth measurement, then the device structure is simple, but the measurement accuracy is poor due to low diffuse reflectance from water bottom and high light absorption/scattering
Solution Approach 1:
The patent divides the scanning process into two distinct phases: a first scanning phase that excludes water surface echoes, and a second scanning phase that captures water bottom echoes. This temporal segmentation allows the system to isolate and process different types of return signals separately, improving measurement accuracy by preventing contamination from strong water surface reflections.
Solution Approach 2:
The patent implements periodic switching between two scanning modes: a first scanning period for excluding water surface echoes and a second scanning period for measuring water bottom depth. This periodic action enables the system to systematically alternate between different measurement objectives, optimizing both accuracy and operational efficiency.
2Measurement precision
If water surface echoes are included in the scanning, then the scanning coverage is complete, but the measurement accuracy deteriorates due to interference from strong water surface reflections
Solution Approach 1:
The patent extracts and removes water surface echoes from the scanning process by implementing a first scanning phase that specifically excludes these interfering signals. By taking out the harmful water surface reflections before processing water bottom measurements, the system prevents signal contamination and improves detection accuracy.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively excluding water surface echoes through a first scanning phase before the water bottom measurement phase. This advance prevention strategy blocks the harmful interference from water surface reflections before they can contaminate the water bottom echo signals.
3Measurement precision
If the laser scanning device is designed for high precision water depth measurement, then the measurement accuracy improves, but the device complexity and weight increase
Solution Approach 1:
The patent makes the laser scanning device multi-functional by enabling it to perform both water surface echo exclusion scanning and water bottom depth measurement scanning using the same hardware platform. This universality allows a single UAV-borne LiDAR system to accomplish multiple measurement objectives without requiring separate specialized devices, thereby controlling weight while maintaining high precision.
Solution Approach 2:
The patent introduces dynamic switching between two scanning modes: a first dynamic scanning phase for excluding water surface echoes and a second dynamic scanning phase for measuring water bottom depth. This dynamic operation allows the system to adapt its scanning behavior in real-time, optimizing measurement accuracy while maintaining a compact, lightweight design suitable for UAV deployment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves water depth measurement accuracy by minimizing interference from stray light and other echoes, reduces device complexity, and facilitates miniaturization and lightweight design for UAV integration.
Implementation Method 1
the diffuse reflectance of light from the water bottom is less than 0.1%
Implementation Method 2
the water body has large light absorption and light scattering
Implementation Method 3
the water body has large light absorption and light scattering
Implementation Method 4
the two-dimensional scanning of combined light spots such as a galvanometer mirror, a polygon mirror or an optical wedge
Implementation Method 5
a photodetector
Data Source
AI summary
A laser scanning device of an UAV-borne LiDAR for water depth measurement, LiDAR, and an UAV are provided. In the laser scanning device, through synchronous driving of two motors, when the incident laser beam completes a 360° light spot scanning process by the rotation of a light-plane reflecting rotating mirror, and a scanning beam is in position ranges of 0°-X° and (360-X)°-360°, a photodetector protection assembly just rotates to an area with a light attenuation value of 0, or an occlusion-free area. Light echoes generated by the scanning beams in the ranges enter a photodetector without attenuation, while the scanning beam in the range of X°-(360-X°) is occluded by a notched circular shield, and stray light generated by the occlusion cannot enter the photodetector due to attenuation of a circular light attenuation sheet or occlusion of an unnotched part of the circular blocking sheet.