LiDAR Range Calibration for Intensity-Dependent Walk Error
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Solution Overview
Problem
Conventional LIDAR devices suffer from 'walk error' due to intensity-dependent range errors caused by varying object reflectivities, leading to inaccurate distance measurements.
Innovation Solution
A calibration target with varied reflectivities is used to generate calibration data, adjusting for walk error by determining the relationship between range errors and reflected pulse intensities, and recalibrating detectors using environmental comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional LIDAR devices measure distance based on time of flight without calibration, then the measurement process is simple and fast, but the measurement precision deteriorates due to walk error caused by intensity-dependent range errors
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual distance measurements. A calibration target with known reflectivities is measured first to establish calibration data, which is then used to correct subsequent measurements. This preliminary calibration step eliminates walk error in actual measurements without adding complexity during operation.
Solution Approach 2:
The patent uses a calibration target as an intermediary object with known reflectivity properties. This calibration target serves as a mediator between the LIDAR device and unknown objects, allowing the system to determine calibration data that compensates for intensity-dependent errors. The calibration target enables accurate measurements of unknown objects by providing reference measurements with known properties.
2Measurement precision
If the LIDAR device uses detectors with high temporal resolution to improve time measurement accuracy, then the time measurement precision is improved, but the reliability deteriorates due to walk error from intensity-dependent range errors
Solution Approach 1:
The patent implements feedback by using calibration data derived from measurements of a calibration target with known reflectivities. This calibration data provides feedback information about the relationship between signal intensity and range errors, which is then used to correct subsequent distance measurements. The feedback mechanism compensates for walk error and improves measurement reliability while maintaining the benefits of high temporal resolution detectors.
3Measurement precision
If the LIDAR device performs calibration using a calibration target with varied reflectivities, then the measurement precision is improved by compensating for walk error, but the loss of time increases due to the additional calibration measurements required
Solution Approach 1:
The calibration process is performed as a preliminary action before actual measurements, allowing the calibration data to be established once and reused for multiple subsequent measurements. This approach concentrates the time investment in a single calibration phase rather than requiring continuous calibration, thereby improving measurement precision while limiting the overall time loss to an initial setup period.
4Device complexity
If the LIDAR device uses a single detector to reduce device complexity, then the device complexity is reduced, but the measurement precision deteriorates due to detector-specific walk error that requires individual calibration
Solution Approach 1:
The calibration target serves as an intermediary that enables precise calibration of individual detectors. By measuring the calibration target with each detector and comparing against known reflectivities, detector-specific calibration data can be obtained. This approach maintains simplicity of the detector system while achieving high measurement precision through individualized calibration for each detector.
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
Accurately compensates for walk error in LIDAR devices, improving distance measurement precision by generating and applying calibration data to correct for intensity-dependent range errors.
Implementation Method 1
detecting, by a detector of the LIDAR device, a reflection of the first light signal from the first region of the calibration target
Implementation Method 2
determining a first apparent range between the LIDAR device and the calibration target based on the detected reflection of the first light signal
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
Example embodiments relate to range calibration of light detectors. An example method includes emitting a first light signal toward a first region of a calibration target having a first reflectivity and detecting a reflection of the first light signal. The detected reflection of the first light signal has a first intensity. The example method further includes emitting a second light signal toward a second region of the calibration target having a second reflectivity and detecting a reflection of the second light signal from the second region of the calibration target. The detected reflection of the second light signal has a second intensity. Still further, the example method includes determining a first apparent range based on the detected reflection of the first light signal, determining a second apparent range based on the detected reflection of the second light signal, and generating walk-error calibration data for the detector.