3D Measurement System Calibration Update Method
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Solution Overview
Problem
Current three-dimensional structured light measurement systems face challenges in accurately compensating for optical non-idealities such as lens geometric distortion, obliquity, rotation errors, and line of sight errors, which can drift over time due to environmental changes, affecting measurement accuracy and requiring time-consuming and complex calibration processes.
Innovation Solution
A method for calibrating three-dimensional measurement systems involving full calibration for each camera/projector pair, generating two sets of correction matrices, and an updated calibration process that measures and updates only the drifting components, facilitating fast run-time processing and accounting for long-term changes, using sinusoidal fringe patterns and simple calibration artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a full calibration is performed for each camera/projector pair to compensate for optical non-idealities, then measurement precision is improved, but calibration time and system complexity increase
Solution Approach 1:
The calibration process is segmented into two distinct parts: a comprehensive full calibration performed periodically to establish baseline correction matrices for all optical non-idealities, and a rapid updated calibration performed frequently to measure and compensate only for drifting parameters. This segmentation allows the system to maintain high measurement precision while reducing the time cost of frequent calibrations.
Solution Approach 2:
The updated calibration performs only partial calibration by measuring and updating only the correction matrices corresponding to drifting non-idealities (such as line of sight errors due to thermal expansion) rather than recalculating all correction matrices. This partial action significantly reduces calibration time while maintaining measurement accuracy.
2Measurement precision
If sophisticated calibration methods are used to accurately calibrate three-dimensional sensors, then measurement precision is improved, but device complexity and calibration time increase
Solution Approach 1:
The sophisticated calibration method is segmented into a one-time full calibration that establishes comprehensive correction matrices, followed by simplified updated calibrations that only measure drifting parameters using simple calibration artifacts. This segmentation reduces the complexity of frequent calibration operations while maintaining high precision through the initial comprehensive calibration.
Solution Approach 2:
The full calibration is performed in advance to pre-calculate all necessary correction matrices for various optical non-idealities. These pre-calculated correction matrices are stored and reused during updated calibrations, eliminating the need to perform complex calibration calculations during frequent calibration operations and thereby reducing device complexity.
3Measurement precision
If full calibration is performed frequently to compensate for drifting non-idealities, then measurement precision is maintained, but productivity decreases due to time loss
Solution Approach 1:
The updated calibration performs only the necessary partial calibration by measuring and updating only the correction matrices for drifting non-idealities rather than performing a complete recalibration. This partial action maintains measurement precision while minimizing the time required for calibration operations, thereby preserving system productivity.
Solution Approach 2:
The system changes the calibration parameters being measured and updated based on which non-idealities are known to drift over time. By focusing only on these specific parameters (such as line of sight corrections for thermal expansion) rather than all calibration parameters, the system maintains accuracy for drifting components while reducing overall calibration time and improving productivity.
Data Source
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Figure 3A~3B
AI summary
A method of calibrating a three-dimensional measurement system having a plurality of cameras and at least one projector is provided. The method includes performing a full calibration (100) for each camera (118, 120, 122, 124) /projector (128) pair where the full calibration generates at least two sets of correction matrices. Subsequently, an updated calibration (200) is performed for each camera(118, 120, 122, 124)/projector (128) pair. The updated calibration (200) changes less than all of the sets of correction matrices.