Coaxial LiDAR Self-Pulse Compensation via Reference Signal
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Solution Overview
Problem
Coaxial LiDAR systems face challenges in detecting objects at low signal levels due to self-pulse saturation and distortion, especially when detecting dark or low reflectivity objects, which results in reduced range performance and accuracy.
Innovation Solution
A scanning LiDAR system that includes a movable optical element with a reflective surface for redirecting optical signals, a reference optical element to generate a self-pulse signal, and a processor to adjust detected electrical signals by subtracting the self-pulse signal, allowing for accurate object detection and improved range performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coaxial LiDAR system is used to detect objects at low signal levels, then the system structure is compact and stable, but the transmit laser pulse saturates and distorts the detector signal making it difficult to detect peaks and close objects
Solution Approach 1:
The patent segments the optical path by introducing a beam splitter that divides the returning light into two separate detection paths: one for detecting reflected objects and another for detecting the self-pulse. This segmentation allows independent measurement and compensation of the self-pulse effect, resolving the contradiction between maintaining coaxial compactness and eliminating self-pulse saturation.
Solution Approach 2:
The patent introduces a reference optical element (light trap) as an intermediary that captures and measures the self-pulse signal. This intermediary component enables the system to separately characterize the self-pulse distortion and apply compensation algorithms, thereby eliminating its harmful effects while preserving the coaxial configuration.
2Use of energy by moving object
If the output laser power is reduced to meet power consumption and eye safety constraints, then power consumption decreases and eye safety improves, but the signal level becomes very low resulting in poor signal to noise ratio
Solution Approach 1:
The patent implements a feedback mechanism where the self-pulse signal is continuously measured by the reference detector and used to dynamically adjust the detection threshold and signal processing parameters. This feedback loop enables the system to maintain high detection sensitivity even at low laser power levels by adaptively compensating for self-pulse effects in real-time.
Solution Approach 2:
The patent replaces traditional mechanical signal filtering methods with electronic signal processing and computational compensation techniques. By using digital signal processing to subtract the measured self-pulse component from the detector signal, the system achieves high signal-to-noise ratio detection without requiring high laser power.
3Length of moving object
If the transmit laser pulse power is increased to improve detection range, then the detection range increases, but the self-pulse saturation and distortion of the detector becomes more severe
Solution Approach 1:
The patent performs preliminary measurement of the self-pulse signal using the reference optical element before processing the main detection signal. By characterizing the self-pulse distortion in advance and storing it as a reference waveform, the system can apply precise compensation to extend the detection range without suffering from saturation effects.
Solution Approach 2:
The reference optical element acts as an intermediary that measures the self-pulse signal at the same optical power level as the main detection path. This intermediary measurement enables the system to scale the compensation appropriately for different transmission powers, allowing extended detection range while maintaining accurate signal processing.
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
The system effectively enhances the detection of objects at low signal levels by mitigating self-pulse interference, improving accuracy and range performance, particularly for dark or low reflectivity objects, and reducing blind areas in both low and high gain environments.
Implementation Method 1
a first movable optical element having an at least partially optically reflective surface for redirecting the optical signal
Implementation Method 2
a detector configured to detect optical energy and generate an electrical signal indicative of the optical energy detected by the detector
Implementation Method 3
The first movable optical element is movable through a plurality of positions corresponding to a respective plurality of directions of the optical signal reflected from the movable optical element, the directions including at least one second direction resulting in the optical signal being reflected from the movable optical element to a reference optical element of the system
Data Source
AI summary
A LiDAR system and method of detecting objects using same includes a plurality of coaxially arranged LiDAR transmitters and detectors. A movable optical element redirects optical signals between the LiDAR transmitters and an external region and reference optical element. The detectors receive returning optical signals after they have deflected off objects in the surrounding environment to generate an electrical signal. A reference signal is generated from the optical signals directed towards the reference optical element. The system determines the position of an object in the external region by adjusting the electrical signal using the reference signal.