Iterative Template Scaling for Calibration Pattern Point Identification
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Solution Overview
Problem
Existing methods for identifying characteristic points of a calibration pattern in images struggle with precision due to unknown scaling caused by varying distances between the camera and the calibration pattern, leading to potential errors in camera orientation calibration.
Innovation Solution
A method that iteratively scales a template arrangement to match the size of the calibration pattern in the image, using a set of candidate points and adjusting the template size based on deviation thresholds and quality indices to ensure accurate identification of characteristic points without requiring explicit distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed-size template arrangement is used for identifying characteristic points, then the identification process is simple and fast, but the precision deteriorates due to unknown scaling caused by varying camera-to-pattern distances
Solution Approach 1:
The template arrangement is made dynamically scalable through iterative adjustment of its size. The system starts with an initial template size and repeatedly rescales it based on the ratio between expected and actual distances, allowing the template to adapt to varying camera-to-pattern distances while maintaining identification precision
Solution Approach 2:
The size parameter of the template arrangement is changed iteratively through rescaling operations. By adjusting the template size based on distance ratios calculated from candidate point distributions, the system compensates for unknown scaling factors and improves identification accuracy without requiring explicit distance measurements
2Measurement precision
If the camera distance to the calibration pattern is explicitly measured to determine template size, then the identification precision improves, but the device complexity and measurement requirements increase
Solution Approach 1:
The system determines the appropriate template size autonomously by analyzing the spatial distribution of candidate points in the image. Through iterative rescaling based on calculated distance ratios from candidate point patterns, the system self-adjusts the template size without requiring external distance measurement devices or additional measurement steps
Solution Approach 2:
The template arrangement serves multiple functions: it acts as both the identification pattern and the scaling reference. By using the same template structure for both matching and size determination, the system eliminates the need for separate distance measurement mechanisms while maintaining precision across varying distances
Data Source
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AI summary
A method for identification of characteristic points of a calibration pattern within a set of candidate points derived from an image of the calibration pattern comprises the steps of: A. scaling a template arrangement of template points which corresponds to the calibration pattern or to a sub-pattern of the calibration pattern to an initial size; B. using the scaled template arrangement for determining potential characteristic points by, for each candidate: (i) overlaying the scaled template arrangement over the candidate point such that a principal point of the template points of the scaled template arrangement coincides with the candidate point, (ii) for each template point of the template arrangement, except the principal point, identifying from the set of candidate points the candidate point closest to the template point, and (iii) determining a degree of deviation by summing or averaging the distances between each template point of the overlaid scaled template arrangement, except the principal point, and the candidate point closest to this template point; and identifying as potential characteristic points of the calibration pattern all those candidate points of the set of candidate points which have a degree of deviation below a deviation threshold; and C. determining whether the potential characteristic points meet a termination criterion and, if the termination criterion is not met: modifying the scaling of the template arrangement and repeating steps B and C with the modified scaled template arrangement, and otherwise: identifying the potential characteristic points identified in the last iteration of step B as the characteristic points of the calibration pattern.