Lidar Detector Field of View Sizing for False Detection Reduction
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Solution Overview
Problem
Lidar systems face challenges in accurately interpreting scattered light due to the potential for erroneously attributing it to the most recently emitted pulse and exposure to excessive light from proximate targets, which can lead to false detections and reduced accuracy.
Innovation Solution
The lidar system configures the light-source and detector fields of view to ensure the detector field of view is larger than the light-source field of view, allowing the detector to move relative to the instantaneous light-source field of view during a scan, ensuring that early returns are ignored and late returns are accurately detected, and uses a cluster of detectors with varying gain to manage high-energy returns from nearby targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detector field of view is made larger than the light-source field of view, then the detector can accurately distinguish between early and late returns from different pulses, but the detector becomes exposed to excessive light from proximate targets
Solution Approach 1:
The patent applies local quality by using a cluster of detectors with varying gain characteristics. Specifically, detectors are arranged with different gain values where detectors closer to the center of the field of view have lower gain to handle high-energy returns from proximate targets, while detectors at the periphery have higher gain to detect weak returns from distant targets. This local differentiation of gain properties allows the system to simultaneously handle both near and far targets without saturation or excessive noise.
Solution Approach 2:
The patent implements dynamics by making the detector field of view movable relative to the instantaneous light-source field of view through scanner synchronization. The detector FOV is dynamically positioned to cover a range that includes both the current instantaneous light-source FOV and future positions, allowing the system to track and distinguish returns from different pulse timing while adapting to the scanning motion.
2Reliability
If the detector field of view moves relative to the instantaneous light-source field of view, then the system can ignore early returns and accurately detect late returns, but the system complexity increases due to synchronized scanning requirements
Solution Approach 1:
The patent merges the functions of the scanner and detector positioning systems by synchronizing their motion. The detector FOV movement is directly coupled to the scanner motion, so that as the scanner deflects the light-source FOV across the field of regard, the detector FOV automatically tracks and maintains the appropriate temporal-spatial relationship. This merging eliminates the need for independent complex control systems for each component.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the detector FOV to cover the range from the current instantaneous light-source FOV to future positions. This anticipatory positioning ensures that when scattered light returns from distant targets, the detector is already in the correct position to capture it, while automatically excluding early returns from the current pulse that would fall outside the detector FOV.
3Measurement precision
If a cluster of detectors with varying gain is used to manage high-energy returns, then the signal-to-noise ratio improves for distant targets, but the device complexity increases
Solution Approach 1:
The patent applies local quality by using a cluster of detectors with varying gain characteristics. Specifically, detectors are arranged with different gain values where detectors closer to the center of the field of view have lower gain to handle high-energy returns from proximate targets, while detectors at the periphery have higher gain to detect weak returns from distant targets. This local differentiation of gain properties allows the system to simultaneously handle both near and far targets without saturation or excessive noise.
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 configuration enhances the accuracy of distance measurements by avoiding false positives and effectively handling high-energy returns, improving the signal-to-noise ratio and reducing errors in lidar systems.
Implementation Method 1
The light source emits light toward a target which then scatters the light. Some of the scattered light is received back at the receiver.
Implementation Method 2
The system determines the distance to the target based on one or more characteristics associated with the returned light. For example, the system may determine the distance to the target based on the time of flight of a returned light pulse.
Data Source
AI summary
A lidar system includes a light source, a scanner, and a receiver and is configured to detect remote targets located up to RMAX meters away. The receiver includes a detector with a field of view larger than the light-source field of view. The scanner causes the detector field of view to move relative to the instantaneous light-source field of view along the scan direction, so that (i) when a pulse of light is emitted, the instantaneous light-source field of view is approximately centered within the detector field of view, and (ii) when a scattered pulse of light returns from a target located RMAX meters away, the instantaneous light-source field of view is located near an edge of the field of view of the detector and is contained within the field of view of the detector.