Lidar Detector System Range Walk Compensation
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Solution Overview
Problem
Lidar systems face challenges in accurately determining the range to targets due to range walk errors caused by differences in target reflectivity, leading to inaccuracies in distance measurement.
Innovation Solution
A detector system within the lidar receiver that detects both the rising and falling edges of a light pulse and calculates the center point, using time-to-digital converters and comparators to determine the range, compensating for range walk errors by considering the pulse's magnitude and reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If range detection is performed on the rising or falling edge of the scattered light pulse, then the range detection process is simple, but range walk errors occur causing targets of different reflectivity at the same range to appear at different ranges
Solution Approach 1:
The patent introduces an intermediary calculation process that uses both rising edge and falling edge detection times as mediators to compute the center time of the light pulse. This intermediary approach eliminates the direct dependency on either edge alone, thereby removing the range walk error while maintaining detection simplicity.
Solution Approach 2:
The patent changes the detection parameter from single-edge detection (rising or falling) to dual-edge detection with center time calculation. By measuring both edges and computing their midpoint, the system transforms the detection approach to eliminate reflectivity-dependent errors while preserving measurement accuracy.
2Device complexity
If only single edge detection is used, then the detector system is simple, but measurement accuracy deteriorates due to range walk errors
Solution Approach 1:
The patent segments the light pulse detection into two separate detection events: rising edge detection and falling edge detection. Each edge is detected independently by separate comparator circuits, and their results are combined to calculate the center time, thereby improving accuracy without significantly increasing system complexity.
Solution Approach 2:
Instead of using a single edge detection point, the patent inverts the approach by using two opposite edges (rising and falling) and deriving the true measurement point (center) from their relationship. This inversion strategy eliminates the systematic error inherent in single-edge detection.
3Ease of operation
If range detection uses single edge detection method, then the processing is straightforward, but reliability of range detection decreases across targets with different reflectivities
Solution Approach 1:
The patent implements a feedback mechanism where both rising edge and falling edge detection results are fed into a center time calculation process. This feedback loop ensures that the final range measurement is based on the averaged information from both edges, improving reliability across varying target reflectivities while maintaining processing simplicity.
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 provides highly accurate range detection across various target reflectivities, ensuring precise distance measurement regardless of target properties, thereby improving the overall accuracy and reliability of lidar systems.
Implementation Method 1
a light source configured to emit light as a series one or more light pulses
Implementation Method 2
detect light scattered by the remote target
Implementation Method 3
produce a representation of a time delay between when one of the light pulses was emitted and a scattered light pulse was received
Data Source
AI summary
A detector system within a lidar receiver is configured to compensate for range walk error by detecting both the rising edge and the falling edge of a received light pulse as the envelope of the received light pulse passes through a particular detection (magnitude) threshold. Detection circuitry within the detector system then determines the center of the received light pulse as the point equidistant in time between the detected rising and falling edges of the received light pulse, and uses the time associated with the center of the received light pulse to determine the range to the target from which the scattered light pulse was received.