LiDAR Receiver Counter-Deflection for Scanner Motion Compensation
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Solution Overview
Problem
Long range LiDAR systems face challenges due to the angle difference between outgoing and incoming laser beams caused by the motion of the scanner and the flight travel time, leading to a large field of view requirement for the receiver, which increases solar background noise and limits scanning speed and resolution.
Innovation Solution
An active device in the receiver optics dynamically counter-deflects the returning light based on calculated angle differences, allowing for a smaller field of view and enabling faster readout and higher signal-to-noise ratio by using smaller detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the field of view of the receiver is increased to collect returning light despite scanner motion, then the returning light can be collected, but solar background noise is strongly increased and detection threshold for weak return pulse signals is limited
Solution Approach 1:
The system calculates the expected beam displacement due to scanner motion during the round trip time, and pre-adjusts the receiver optics position or field of view orientation before the returning beam arrives. This preliminary action ensures the receiver is already positioned to capture the returning light, eliminating the need for a large field of view and thus reducing solar background noise while maintaining detection sensitivity.
Solution Approach 2:
The system continuously monitors the scanner position and timing information, uses this feedback to calculate the current beam displacement, and dynamically adjusts the receiver optics accordingly. This closed-loop feedback mechanism ensures the receiver remains precisely aligned with the returning beam despite scanner motion, maintaining a narrow field of view and minimizing solar background noise.
2Reliability
If the field of view of the receiver is increased to collect returning light, then the returning light can be collected, but the readout time of the detector is increased and scanning speed is limited
Solution Approach 1:
The receiver optics are pre-positioned based on predicted beam displacement from scanner motion, ensuring the detector is already in the optimal position to receive the returning light. This eliminates the need for a large field of view, allowing the use of smaller detectors with faster readout times, thus increasing scanning speed while maintaining light collection efficiency.
3Reliability
If the field of view of the receiver is increased to collect returning light, then the returning light can be collected, but the detector bandwidth is reduced
Solution Approach 1:
The system pre-calculates and pre-adjusts the receiver optics position based on expected beam displacement from scanner motion. This allows the use of smaller detectors with narrower fields of view, which have higher bandwidth capabilities, while still maintaining efficient light collection through precise positioning.
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
This solution improves signal-to-noise characteristics, increases scanning speed, and enhances scanning resolution while reducing the technical and cost burden of sensor electronics.
Implementation Method 1
an active device in the receiver optics dynamically counter-deflects the returning light
Implementation Method 2
short laser pulses are transmitted and directed towards a target surface
Implementation Method 3
when it returns after the reflection on the ground
Data Source
AI summary
A system for compensating for an angle difference between outgoing and incoming beams of a scanner in a long range LiDAR surface scan, the angle difference being dependent of the flight travel time of the beam and of a movement of a deflection unit of the scanner. The scanner consists of a transmitter unit emitting laser pulses, a movable deflection unit directing the laser pulses towards a target surface according to a given scan pattern, a receiver unit, comprising of receiving optics and a photo-sensitive time-of-flight sensor, and a control unit. The receiver unit comprises an active device for compensating for the angle difference between outgoing and incoming laser pulses and the control unit actuates the active device of the receiver unit and calculates a predicted angle difference between outgoing and incoming laser pulses based on a prediction of the time difference between the outgoing and incoming laser pulses.