Varied-Density Calibration Chart for Single-Image Camera Calibration
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Solution Overview
Problem
Existing camera calibration methods require multiple images to achieve high diversity, complicating automated calibration processes due to redundant information and inefficient data utilization.
Innovation Solution
A calibration substrate is tilted at an oblique angle to the camera, featuring a sparse grid in the distant region and a dense grid in the closer region, with QR codes for automated pose estimation, allowing calibration with a single image by providing diverse data points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a uniform dense grid is used across the entire substrate, then more calibration data is available in the near region, but grid corner detection becomes difficult in the distant region and redundant information is captured in the near region
Solution Approach 1:
The patent applies local quality by implementing a varied density grid where the grid spacing is not uniform across the substrate. Specifically, the grid is denser in the near region (closer to the camera) and sparser in the distant region. This local adaptation optimizes each region's grid density to match its specific calibration needs, providing sufficient data points where required while avoiding redundancy and detection difficulties in other areas.
2Measurement precision
If multiple calibration images are taken to provide high diversity, then calibration accuracy is improved, but the automated calibration process becomes more complex
Solution Approach 1:
The patent segments the calibration substrate into distinct regions (near region and distant region) with different grid densities. This segmentation allows a single image to capture sufficient calibration data from both regions simultaneously, eliminating the need for multiple images. The near region provides dense data points for accurate camera parameter calibration, while the distant region provides diverse geometric information, together achieving high calibration accuracy in one shot.
Solution Approach 2:
The patent tilts the substrate at an oblique angle relative to the camera's optical axis, introducing a dimensional change from a front-facing to a tilted configuration. This tilt creates a more diverse range of geometric relationships and perspective variations in a single image, effectively capturing calibration information that would otherwise require multiple images taken from different positions or angles.
3Extent of automation
If QR codes are placed in all grid regions, then automated pose estimation is enhanced, but the substrate becomes more complex and harder to manufacture
Solution Approach 1:
The patent applies local quality to QR code placement by positioning them only in specific regions (primarily in the distant region and selectively in the near region) rather than uniformly across the entire substrate. This selective placement provides sufficient automated pose estimation capability while reducing the total number of QR codes, thereby simplifying manufacturing compared to a full-coverage QR code arrangement.
Data Source
AI summary
A chart for camera calibration is tilted away from the camera. The part of the chart that is further from the camera has a relatively sparse grid to make finding grid corners easier, whereas the part of the chart closer to the camera has a relatively dense grid to provide more data for better calibration.